It depends...you can text chat with other players in a multiplayer game. SHIFT+TAB toggles the chat line, ESC cancels the chat line, and TAB cycles the chat between team/enemy/all. SHIFT+1 through 4 will also store and recall up to 4 custom messages.
If it's voice chat you want, none of the multiplayer games in the series (XvT/BoP and XWA) support it, but a third-party application called TeamSpeak
is popular for this purpose.