IceWM is a windows manager graphical user interface (GUI) for the open-source X Window System, a technology that allows GUI development in networked computers. The IceWM GUI provides a light build along with customizable features, and runs on various operating systems, including Linux and Windows. The system requirements for successful operation are fairly minimal.
Techopedia explains IceWM
IceWM is compatible with GNOME and other elements of Linux. Users have taken advantage of IceWM for a lighter Ubuntu build, or in other situations where the simplicity of the GUI helps to accomplish a specific design goal. IceWM can also run on much older machines than some other types of interfaces; users have even reported that it can run successfully on an obsolete 386 computer.
Another feature of IceWM is the ability to manage commands using the keyboard. The program generally relies on a command line structure, whereas some other GUI options rely on a more visual interface.