Oversimplified, Plug-and-Play automatically tells the software (device drivers) where to find various pieces of hardware (devices) such as modems, network cards, sound cards, etc. Plug-and-Play's task is to match up physical devices with the software (device drivers) that operates them and to establish channels of communication between each device and its driver. In order to achieve this, PnP allocates the following "bus-resources" to both drivers and hardware: I/O addresses, IRQ's, DMA channels (ISA bus only), and memory regions. It's not the intent of this help to make you a Plug-and-Play guru. You can find more information about it in 'Plug-and-Play-HOWTO'.