/cb
Display a chat bubble message above their head to players who are near (in white)
In the game
Usage: /chatbubble <Message>
Displays the specified message in a chat bubble above your head (in white).
Players that are within 40 metres of you will see the message above your head and in the chat text area.
Note: you cannot see your own chat bubble on your screen... only other players see it.
The shortcut for this command is: /cb or use the - character.
What it does
Not explained in detail yet.
Wiki