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.
rxvt-unicode is a clone of the well known terminal emulator rxvt, modified to store text in Unicode and to use locale-correct input and output. It also supports mixing multiple fonts at the same time, including Xft fonts, real transparency, and an optional embedded Perl interpreter that allows you to extend your terminal easily.
xtermcontrol enables dynamic control of XFree86 xterm properties. It makes it easy to change colors, titles, fonts, and the geometry of a running xterm, as well as to report the current settings of the properties. Window manipulations such as (de)iconify, raise and lower, maximize and restore, and reset are also supported. It also lets advanced users issue any xterm control sequence.