Personal computers (PCs) are one of the many platforms on which games run. They include laptops & desktop computers running various operating systems, such as any Linux variant, Mac OS X or Windows.
They differ from video game consoles in that consoles are sold as embedded systems with static hardware that allow for development against a consistent environment. Pieces of PC hardware are more easily upgraded individually, but result in many different environments against which companies develop games.
Questions in the PC tag often involve either issues involving PC-only features of a game or issues running a game in a PC environment. These issues can be caused by hardware or other software specific to computers.