Short for fanfiction
. Unlike fanfiction, the word fanfic (also just 'fic') is a single noun (pluralized as 'fanfics').
A story written by a fan of a particular ard
(movie, book, tv show, video game, etc.), about the characters and world in that series, usually without the original creator's permission.
By the very nature of fanfiction, there're a lot of really terrible fics out there. But when you find a good one - it's great!