The RPC is used to communicate with a running Wasabi instance. It provides some options and features which are not available (yet) when using the Graphical User Interface. Since Wasabi version 2.0.6, the RPC can be exposed as an onion service, which enables remote control.

Think of it as your wallet but on a diet. It uses fewer resources like CPU, GPU, memory, and bandwidth, allowing you to run Wasabi Wallet unobtrusively in the background.