What is the difference between round and flat characters exactly. I think i know a little but i am a bit confused.

Answer 1

Flat characters are two dimensional. They do not develop. The reader does not know what they are feeling or what they want; they are pretty much there for the "round", "developing" character to play off of. The round character develops, changes, as the story develops. The story is about this growth.

Answer 2

Round characters are the main characters the author tells us a lot about. We feel that we really know them. Flat characters are more like acquaintances. The author doesn't tell us much about them so we don't feel we know them.

Check this site for more information.

http://fictionwriting.about.com/od/glossary/g/RoundCharacter.htm