Plug and Play (or it's TLA, PnP)refers to the ability of a computer system to automatically configure expansion boards and other devices. You should be able to plug in a device and play with it, without worrying about setting DIP switches, jumpers, and other configuration elements. Since the introduction of the !NuBus?, the AppleMacintosh has been a plug-and-play computer.
In an attempt to resolve this ongoing problem, the Plug and Play (also called PnP) specification was developed by MicrosoftCorporation with cooperation from Intel and many other hardware manufacturers. The goal of Plug and Play is to create a computer whose hardware and software work together to automatically configure devices and assign resources, to allow for hardware changes and additions without the need for large-scale resource assignment tweaking. As the name suggests, the goal is to be able to just plug in a new device and immediately be able to use it, without complicated setup maneuvers.
A form of Plug and Play was actually first made available on the EISA and MCA buses many years ago. For several reasons, however, neither of these buses caught on and became popular. PnP hit the mainstream in 1995 with the release of Windows 95 and PC hardware designed to work with it.
It never really used to work; its early code name was (of course) plug-and-pray.