What do people mean when they say "Fanfiction"?
Exactly what it sounds like. Fanfiction is fiction written by a fan (or more) of a series. Sometimes it may have more than one television series involved.
Your handle is "scifigeek" and you don't know what fan fiction is? Surrender your nerd card!
Something (usually a short story) that was made by a fan and not the people that originally made it. Based on a show, book, video game, etc.
horaquankiller is right.... so is the silent ninja...... I am writing a LOTR fanfic right now and I have made my own characters......