Fanon

Fanon is unofficial work not endorsed by the author / creator of a book, film, video game, etc. It is the opposite of canon.

Alex Rider Fanon[]

Fan art, fan fiction, and original characters are all considered fanon works in the Alex Rider universe.

Fan Fiction (also known as fanfiction, ff, and fanfic) is a term given by fans to fictional work they have done for literature, movies, video games, etc. The work is unofficial and is usually placed on the internet with a disclaimer stating what the fan owns and doesn't own.
Original Characters (or OC's) are non-canon characters usually created by a fan for fan fiction.
Fan's are admirer's of a piece of work.
Fan Art is unofficial art created for a book, film, video game, etc.
A Universe is the plane of existience that the book, film, video game, etc. take place on. Most often each work will have a separate universe lest the events that take place accidently effect a work that had nothing to do with the event.
Crossover's are fanfictions where one or more universes are brought together. Often the main characters of each work will then join forces to defeat some foe.
Fandom's are groups of fan's that partake in activities showing their dedication to a work, such as writing fanfiction and creating fan art. It is a mix of the words "fan" and "kingdom."