What is the meaning of 'cool' generally used in chating?

If your definition of "chatting" includes informal conversations either in-person, over the phone, or through technology (email, text message, instant message, etc.), my experience is that the word "cool" is used to indicate agreement, acceptance, or confirmation. For example:
"Cool?" - Do you agree with me?
"Cool." - That's fine by me.
"Cool!" - You're right!