PS/2 was originally the name of a new range of IBM PCs which were not IBM PC compatible. IBM tried to reclaim the PC market from the clones with this move. Instead, it cost them whatever dominance they had left. Nowadays the term is used to refer to the compact connection ports for keyboards and mice introduced with the IBM PS/2 line of computers, as opposed to the much larger XT/AT ports for keyboards and the serial connectors for mice. Now largely replaced by USB peripherals.

Depending on BIOS support for USB you may still need so-called "legacy" PS/2 input devices to interact with your BootLoader and the BIOS setup.