This is the process that makes this device available as a networked endpoint that can play audio. It’s always running but rarely doing anything unless you are playing audio to a directly-attached (typically USB) DAC.
This is Roon (the program) which on Windows and Mac can act as a Core, Remote, and/or output device. Roon will also startup RAATServer.
This is the equivalent program to Roon (the program) which comes along with the RoonServer software. It’s the main process that kicks off all of the others (RAATServer and RoonServer). Depending on your OS and how you’re looking at processes this one may show as the one using a lot of resouces (since it’s the parent process).
This is the portion of the RoonServer installation that handles all of the Core functions (library management, Tidal, DSP, etc). This is typically what’s actually eating up CPU on the Core.