OOC means 'out-of-character', meaning when you talk about/comment on things happening in an RP as yourself rather than in the role of your RP character. It's a convention that's there to prevent confusion over what part of a post is something the RP characters should react to and what isn't. OOC discussion is...well, discussion that occurs out of character, obviously. Pretty much just casual chit-chat about an RP.
Umm...I hope that clarified?
Umm...I hope that clarified?