This article is from the GNU Chess and XBoard FAQ, by Tim Mann firstname.lastname@example.org with numerous contributions by others.
XChess is an older chessboard program that is no longer supported.
XChess was written for X version 10, and you may or may not be able to
build and run it on an X11 system.
XChess has only one significant feature that is not present in XBoard:
Two humans can play chess using XChess on different machines, without
using the Internet Chess Server as an intermediary. This feature is of
interest only if you don't have network connectivity to the Internet
Note: There actually have been several different programs called
"XChess" in circulation at various times. The above describes one that
was associated with GNU Chess.