Easy way to remember it:

Anything outside of 2 days is automated PCS: WS, SS, PD, APD, IVD, VAS, recovery slips, X-day, SwP (NOT A PROFFER, system assumes that you are watching what you do).
This is the "auto PCS" and is run entirely by the computer. No scheduler looks at or touches it. You can see the sequence "auto" PCS operates in 23 E.2. When you hear "runs in PCS" it almost always means the "prior to 2nd day" automatic PCS functions. This is the system that runs 4 times a day at set times.

Anything inside of 2 days* is manual coverage and is mostly done on a proffer basis. You put your requests in PCS (makes that nice and confusing), but they are handled by Crew Scheduling. Follows 23 N & O ladders. The only time the coverage ladders come into play is 2nd day, next day, same day. When you hear the phrase "trip coverage" or "rotation coverage" it is almost always talking about the 23 M. (think M for manual) manual trip coverage sequence. Filling of trips during this period effectively happens when it happens.

*You can check a box to be included on the 0700 run on 2nd day.

*Leave type auto PCS (APD, PD, etc) as well as SwtP continues to run inside 2nd day.

Pilot to Pilot Swap for rotations and X days is completely automated. No scheduler looks at it. Executed instantly. Run by a completely different system.

Jetway trades are semi-manually handled by CS.