It describes itself as a server-side application for playing music, but it can be used locally as well. For example, the Cantata music player uses mpd to handle music decoding and playback, but automates it in the background to keep the interface simple for the user. This separation of concerns allows Cantata to benefit from things like decoding improvements, security fixes, and new sound APIs (e.g. PipeWire) without having to reinvent the wheel.