The Chatbox commands allow you, for an example, to delete messages, ban or unban a member, etc. They are to type in the "message" block, as you were posting a message.
/clear : Delete the messages from the Chatbox
/cls : Same as the '/clear' command
/ban : Ban a member from the Chatbox
/unban username : To unban a user from the Chatbox
/me : this command will be replaced by your username
/kick username : Disconnect a member from the Chatbox.
/exit reason : Disconnect from the Chatbox.
/abs reason : Send a message noticing that you're absent.