In computing, ‘plug and play’ describes the joint capability of plugging devices to a computer and getting them running without configuration effort. Its a feature that, both, the hardware (the device) & software (usually a driver or operating system) The software is capable of discovering & getting the hardware ready to use; and to do this the hardware provides necessary information. USB devices are a classic example, but the term was more popularized by Microsoft to market the ability of its Windows OS to configure devices.
This term is also used by sales teams to market software and emphasize its ease of installation/deployment, configuration/implementation and quicker Go Live! However, this is not always the case! My boss once told a vendor that not matter what sales calls it, to customers its usually ‘Plug-and-Pray’ 🙂