In online poker, the chat box is a designated area usually located at the bottom left or right of the screen, which enables you to communicate with other players at your table.
You can use the poker chat box to talk to your opponents and confuse them. Just keep in mind some opponents disable the chat box.
You can also get alot of information for all sorts of reasons by observing the online poker chat box. It is easy to tell what kind of mood a player is in and how they approach the game. This additional information can help you to form better reads.