WirePlumber is a modular session / policy manager for PipeWire and a GObject-based high-level library that wraps PipeWire's API, providing convenience for writing the daemon's modules as well as external tools for managing PipeWire.
The WirePlumber daemon implements the session & policy management service. It follows a modular design, having plugins that implement the actual management functionality.
The WirePlumber Library provides API that allows you to extend the WirePlumber daemon, to write management or status tools for PipeWire (apps that don't do actual media streaming) and to write custom session managers for embedded devices.
The latest version of the documentation is available online here