Switch your chat to global chat! Speak freely with everyone on the server! (or don't, we can't force you).
Toggle your ability to see global chat! You can choose to see or not see what everyone is saying.
Switch your chat to local chat! Speak freely with other players in ~100 block radius of you.
Switch your chat to town chat! Speak freely with other citizens of your town.
Privately message with other players!
Respond quicker to a private message from another player! (This will reply to the last player that messaged you).