Correspondence chess is chess played by various forms of long-distance correspondence, traditionally through the postal system. Today it is usually played through a correspondence chess server, a public internet chess forum, or email. Less common methods that have been employed include fax, homing pigeon and phone. It is in contrast to over-the-board (OTB) chess, where the players sit at a physical chessboard at the same time; and most online chess, where the players play each other in real time over the internet. However, correspondence chess can also be played online.