For many of 30-somethings and under, the "Harry Potter" series was a sort of a gateway drug. Many children were encouraged to read the books due to their astounding popularity, extensive and fascinating world-building, likable characters and engaging plot. Personally, my mom read me "The Sorcerer's/Philosopher's Stone" when I was around six or seven, starting off a slippery slope that lead to a dangerous obsession by the time I was in the second grade. (In retrospect, my fascination with fandom culture and my descent into nerdom were probably inevitable.)

Hold on to your hats, your cloaks and your wands, ladies and gentlemen, witches and wizards, because this fandom is vast and diverse and loving of the best-selling book series of all time.

Subject: The "Harry Potter" series, films and fandom

"Harry Potter" was first dreamt up by Joanne Kathleen "J.K." Rowling on a Manchester-London train in 1990—a big story about a small boy with round glasses who becomes a wizard. After sending the story to several agents, she was represented by Christopher Little, but was then rejected by eight publishing companies. "Harry Potter and the Philosopher's Stone" was then picked up by Bloomsbury and published in the UK on June 30, 1997, and released in America on September 1, 1998, although it was published with alteration of the title, from "philosopher's stone" to "sorcerer's stone". 

Since that first inkling of an idea, there has been seven novels, eight film adaptations, 400 million copies sold and an additional 400 related products. The brand itself is believed to be worth up to $15 billion. 

Since then, the books have been compared to J.R.R. Tolkein's "The Lord of the Rings", C.S. Lewis' "Chronicles of Narnia", and Roald Dahl's classic children's books.

As the series progressed, the target age group moved up and the plots darkened significantly. While the storyline was always somewhat dark to begin with—an orphaned boy living with an abusive aunt and uncle is not exactly "lighthearted"—the storylines began to take on themes of prejudice, genocide, sacrifice for the "greater good", the role of an individual versus the duty to one's community, governmental and societal corruption, as well as notably violent, cruel or fatal passages in which beloved characters were killed off suddenly. 

While the series has had both negative and positive reviews, it is a huge part of many young adults' and children's lives. It has been praised for encouraging children to read, especially as we continue to become more dependent on visual media rather than word. Translated into over 100 languages, this passion for all things Potter has spread worldwide over the past decade and a half. 

Fandom name: Most often called "Potterheads", although there are some (often inappropriate) tongue-in-cheek variations 

While most certainly not the oldest fandom, it is one of the most extensive and the most diverse. It continues to be one of the most active fandoms, in spite of its relative youth. Because many fans felt they "grew up with the series", they consider it to be a large part of their childhoods. 

In some ways, "Harry Potter" evolved beyond a series of "children's" books (which is an arguable designation when taking into consideration the subject matter, and the continued appreciation of the novels for teens and adults.) For many, it's more of a lifestyle; it's an inherent part of the way they view themselves and see the world. Because so many children were encouraged to love reading because of these novels, to let their imaginations develop and grow and to create attachments to the characters and storylines, many people consider "Harry Potter" to be their first fandom. Through their passion for the series, they were introduced to similar fantasy novels; they read and wrote and imagined themselves in the stories. 

But instead of similar fixations with subject matters, this fascination never fell away for vast numbers of children. Hence, the creation of a wildly popular and extensive fandom.

Fandom activity: Conventions, marathons, game tournaments, meet-ups, costly, Pottermore, games, trivia, panels and book signings, Wizard Rock (sometimes called Wrock, although that also denotes a separate genre of music), Quidditch tournaments, classes and more

With such a plethora of material to investigate and enjoy, Potterheads have much to go through. The seven novels themselves are lengthy, and while they may be addictive, they're not all there is. Extra-canonical work, such as Rowling's additional novels, "Fantastical Beasts and Where to Find Them", "Quidditch Through the Ages" and "The Tales of Beedle the Bard" can be purchased, and much of the payment goes to charity. 

Each of the films has a video game based off it; additionally, the LEGO "Harry Potter" games are widely played. While the games are usually one-to-two players only, there are occasionally small meet-ups and tournaments. 

In addition, Comic-Con and nearly every other multi-fandom meet-up has at least a few Hermiones, Harrys, Rons and the like; Potter-specific meet-ups are not uncommon either, especially centering around film or book releases, Q&As, panels and book signings. Any time new information, a new interview or press statement is made, the Potter fandom rises anew, and with incredible fervor. The Potter fanaticism may rise and fall, but it never disappears. Other fandoms, after films or books have been completed and it becomes evident that no new material will be written in the near future (if at all), will fall into dormancy. Not so with the Potter fandom.

It's possible that the nearly incessant ABC Family "Harry Potter" film marathons have something to do with it. Almost every holiday coincides with one of these marathons, to the point that the network might be better off just having nonstop marathons at this point. 

Pottermore is the Rowling-sanctioned fansite that places players into their houses, gives them a wand based off quizzes and their personality, and is the most in-depth and inclusive Potter-world available on the Internet. Sign-up is free, and it features interactive and previously unseen content from Rowling herself. 

Alternatively, you can go to the "Wizarding World of Harry Potter" theme park in Orlando, Fla., where you can go on rides, buy wands and robes, eat foods both mentioned and inspired by the novels and generally live every fan's dream. 

High school and colleges all across America and the UK (including USC) have organized Quidditch teams. These teams, like other sports teams, occasionally travel cross-country for tournaments. For information about the sport, check out the site here. 

How does one play Quidditch without use of magical flying broomsticks, you may ask? I respond completely seriously: by running around with a broom between your legs. The Golden Snitch is played by one person, not pertaining to either team (occasionally, snitches switch off). Official rules dictate that the snitch must respect pre-set boundaries, and will run wherever he or she likes within those boundaries. While the other players keep their eyes closed, the snitch will run off, generally for five minutes. The game ends when the "snitch" is caught, or tagged, by one of the team's Seekers, provided that there is no tie. In addition, the teams must be coed and player positions are denoted by headband colors; the snitch runner must be in all yellow. Provided he or she notifies all officials prior to the game, the snitch can use anything from a bicycle to water balloons to evade Seekers, even going off pitch.

If you're less athletic and more musical, Wizard Rock may be up your alley. (I could not think of an appropriate pun.) This is an entire genre of music solely dedicated to writing for and about "Harry Potter". Most of it can be found on Youtube, and some can be purchased on iTunes, downloaded (for free or with payment) on the bands' websites.

Good people to know: J.K. Rowling, Emma Watson, Daniel Radcliffe, Rupert Grint, Tom Felton, Alan Rickman and the rest of the film casts, individual characters (no, I will not name each one), Cassandra Claire, Steve Vander Ark, Makani, Neil Cicierega, Emerson Spartz, Darren Criss and Starkid

J.K. Rowling, the author, and the actors and characters make quite a bit of sense, but due to the depth and range of the fandom, several fans have ascended, some even having their own fandoms.

Cassandra Claire (also Cassandra Clare), is a former-fanfiction writer for the "Harry Potter" community, until she was accused of plagiarism from several literary and screen sources, and was then banned from several fic hosting sites. She is also known as the author of the popular "City of Bones" series, which will soon be made into films. 

Steve Vander Ark is the author of the Harry Potter Lexicon, an online encyclopedia of "Harry Potter" and had details of the world. Rowling approved of the site until they published a book without permission; the Lexicon has since fallen out of favor. More favorably, Emerson Spartz, the creator of Mugglenet, is well-known and has interviewed J.K. Rowling and helped writing to (approved) Potter-based books, both best-sellers. 

If fanart is more your game, look up Makani, who is also notable within the "Team Fortress 2" video game community; her art served as the inspiration for a character and then was later hired by the company Valve for her artwork. 

Even if you're not active in the "Harry Potter" community, you'll be familiar with Neil Cicierega's wildly popular "Potter Puppet Pals" series (note: often NSFW). Occasionally animated, occasionally live-action, these shorts are loving parodies of the series.

Meanwhile, if you're more into musical theater, check out "A Very Potter Musical", and its sequel, "A Very Potter Sequel". You may recognize Darren Criss, who is now known for playing Blaine Anderson on "Glee" and for singing at the recent presidential inauguration. While at the University of Michigan in 2009, Criss wrote the music and lyrics and Starkid Productions, the theater troupe, produced and performed a full musical (affectionately) poking fun at the novels, which became popular. Shortened to "AVPM", the entire musical can be found on Youtube under Starkid's Youtube channel or can be purchased on iTunes. Starkid Productions has since created other musicals, and has a third installment of the AVPM series was performed at the Harry Potter convention LeakyCon in August 2012; the videos and album is set to be released at the end of February 2013. Entertainment Weekly named the musical one of the "10 Best Viral Videos of 2009". 

Some wise words to know: Potterhead, Quidditch, Hogwarts, muggle, Lord Voldemort, Death Eater, Ministry of Magic, Auror, the houses, The Boy Who Lived

Potterhead: a fan of the books, the films—really anything related to the Potterverse.

Qudditch: A popular wizard sport played on flying broomsticks. Alternatively, an adaptation of the sport played in real life (see above). 

Hogwarts School of Witchcraft and Wizardry: Home for most fans. It is the school Harry and his friends attend (or, post-novels, attended.) If you do not know what this is, you have lived under a rock the stairs for most of your life. 

Death Eater: The followers of the megalomaniacal, genocidal Lord Voldemort, otherwise known as He-Who-Shall-Not-Be-Named/You-Know-Who. They have dual aspirations to take over the wizarding world and kill off all Muggles. 

Muggles: Non-magical folk. They are unaware of the magical community and many wizards and witches are unfamiliar with Muggle-ways, such as the use of cars, electricity, pens, and non-wizard clothing. I refuse to submit to the idea that I am a Muggle. My Hogwarts acceptance letter is simply late. 

Ministry of Magic: The wizard government, which is a subset of the British government that remains autonomous and handles all wizarding affairs. Supposedly, the prime minister is aware of its existence, although knowledge is limited. Many of the adults in the novels work within the government. The Minister of Magic is the head of all magical affairs.

Auror: One of the magical defenders—sort of like a policeman, these people are particularly skilled duelists, practiced with defenses against the dark arts, and are dedicated to protecting the wizard public. 

The Hogwarts Houses: New Hogwarts students will sit under the knowledgeable Sorting Hat, which, after a somewhat egotistical ditty, will search through the student's mind, heart and soul to discover where he or she truly belongs. Gryffindor, the home of the courageous and the brave, is Harry, Ron and Hermione's home. Hufflepuff is the house of the faithful and loyal students. Their loyalty is hard-earned but for forever. (Rowling herself has stated that she's a Hufflepuff.) Ravenclaw students are known for their sharp wit and clever minds, and are dedicated to their interests and intellectual pursuits. Slytherin students, often unfairly maligned for being cruel or "evil" characters, are truly ambitious and cunning. There are exceptions to each house. To find out which house you belong to, check out Pottermore or take one of the less-official tests. I'm a Ravenclaw. 

The Boy Who Lived: Harry Potter himself, who survived Lord Voldemort's Killing Curse (Avada Kedavra—one of the forbidden spells) as a baby, became famous within the wizarding community and is our story's hero. 

Happy homes for the wayward fan: For info, you can check out Pottermore, Mugglenet, the Leaky Cauldron online, the Harry Potter Lexicon, Harry Potter Fan Zone, the Harry Potter Alliance (a fansite that relates real-world problems to the books), TheHPFan, the Harry Potter Wikia and TVTropes page, or check out any of the novels or extracanonical books available at bookstores or for e-reader. 

There are also several regular podcasts available on iTunes, including "MuggleCast" (run by Mugglenet) and "PotterCast" (run by The Leaky Cauldron). There is also "Hogwarts Radio" and "Snapecast" focuses solely on Professor Severus Snape's character. The most recent one is "The Potter Pensieve".

And now, for some curious miscellany: 

Any joke about Hufflepuffs: Usually these relate to the supposed "dimwittedness" of Hufflepuffs.  Hufflepuffs aren't actually stupid, but God is it entertaining to make fun of them for it. Also, the mascot of the Hufflepuffs is a badger. Honey badger don't care. 

Yer a wizard, Harry: This iconic line has been twisted and turned every way, applying to nearly every fandom. For example: "Yer the Mockin'jay, Katniss" for the "Hunger Games". 

Snape jokes: "After all this time?" is a phrase that should always be followed with "Always". Also, Snape puns. 

Why do social networks always seem dead on Sundays? Answer: No post on Sundays. 

Draco Malfoy and Lord Voldemort hug. It's the most awkward hug in existence.

Read "My Immortal", even if you have no desire to ever read fanfiction, ever. It is possibly the worst fanfiction in existence—between the frankly unintelligible grammar, the awful spelling and the ridiculous plot, it makes it cringeworthy and absolutely hilarious at once. It's awful. 

Draco in Leather Pants: Now a TV Trope, a term that references a villain or antagonistic character who often is retooled by fans to make him more empathetic or desirable.

Ten points from/to Gryffindor: Anytime someone does something good, award the posts. Alternatively, remove ten points. When someone does something inexorably stupid, you might need to take away more points. Or take away points from Hufflepuff for an added barb. 

Cedric Diggory: [spoiler] Cendric Diggory is a character played by then-newcomer Robert Pattinson. He dies at the end of "Goblet of Fire"...and becomes Edward Cullen? A bit of a downgrade, but to each his own. Cedric dazzles me. Also, he just happens to be a Hufflepuff.  

Lord Voldemort's missing nose and hair. No further explanation needed.

Next week, we'll take a look at the "Star Trek" fandom, in honor of the upcoming movie. From here on out, we'll be working on these fandom-specific guides for your convenience. 

Reach Columnist Christine Bancroft here or find her on Twitter here. She can also be found sobbing quietly over the end of the series, reffing Quidditch matches, or questioning Pottermore's decision to place her in Ravenclaw when she is obviously a Ravenclaw/Hufflepuff hybrid.