What's a furry?
To some folks, funny-animal game characters and popular TV show characters qualify as furry. This includes characters such as Sonic, Tails, Knuckles, Rogue, the various pokemon, Starfox, and perhaps most notoriously Minerva Mink, Krystal, and Renamon.
To others, it's a much narrower list of usually original characters.
Regardless, it's kinda' hard to define and varies from person to person..
Oh, and furries are also people who are fans of furry characters, including of their own characters.
The best articles describing it far more eloquently than I can:
The furry fandom as defined by the largest furry convention to date, Anthrocon.
Furry as defined by WikiFur.
The furry fandom as defined by Wikipedia.
(It's hard to determine which entry came first, Wikipedia's or WikiFur's.)