What “Chat” means
Chat means to talk, and it often hints at talking too much. "Chat bout" means to discuss something. It's a general word for speaking, not only light conversation.
Examples
A who dat man yuh did a chat to?
Who is that guy you were talking to?
Yuh chat too much!
You talk too much!
How to use it
Common everywhere. "Yuh chat too much" is a familiar complaint, half teasing, half serious.
Cultural context
In sound system culture, deejays "chatting" rhythmically over instrumental records helped create toasting, a forerunner of rap.