The xterm program is the standard terminal emulator for the X
Window System. It provides DEC VT102/VT220 and Tektronix 4014
compatible terminals for programs that can't use the window
system directly. If the underlying operating system supports
terminal resizing capabilities (for example, the SIGWINCH
signal in systems derived from 4.3bsd), xterm will use the
facilities to notify programs running in the window whenever it
is resized.

WWW: http://invisible-island.net/xterm/