rxvt-unicode is a customizable terminal emulator forked from rxvt.
License: Open Source
xterm is the standard terminal emulator for the X Window System. A user can have many different invocations of xterm running at once on the same display, each of which provides independent input/output for the process running in it (normally the process is a Unix shell). Developed by Thomas E. Dickey
License: Open Source
rxvt-unicode is a lightweight terminal emulator known for its customization options, including support for transparency and tabs, making it ideal for modern desktop environments. In contrast, xterm is a more established terminal emulator with a rich feature set and better accessibility, though it may be heavier on resources and lacks some modern features.