'Fursuit' is another name for an animal costume, generally
referring to one intended to be as realistic as the maker can achieve,
although 'mascot'-style costumes are often included, and some furries
have/wear/make both.
Some furries like a more 'toonish' type of fursuit. Not a
mascot, but something that is as close to some of their favourite
toon
fantasies as possible. It's rather like trying for realism where the
desired goal is an already
anthropomorphic character.
By putting on a fursuit, you _become_ a furry, as close as
you'll get without surgery, anyhow. But BE WARNED; not everyone in an
animal costume is a furry!
Many furries feel that donning a fursuit helps them move
closer to their 'true' furry form, and it's not at all unusual for
furries to spend a lot of time in their suits, including sleeping in
them. It has been reported by some furries that making love in a
fursuit can be... very furry indeed!