In the v20.2 Infinite Flight update comes a subtle change to the way Check In and Flight Following are shown on the pilots end and a small procedure change. Changes that will hopefully make it more clear as to what the uses of check in and flight following are for.
Check In (IFR)
Check In is a request for IFR service from ATC. Pilots are expected to follow their filed route in the absence of ATC-assigned headings, altitudes, and speeds. ATC is responsible for aircraft separation from aircraft and terrain.
Flight Following (VFR)
Flight Following is a VFR service that can be requested by a pilot with or without a flight plan. Pilots are expected to see and avoid other traffic and may be subject to ATC altitude and heading assignments. VFR aircraft with a filed flight plan are expected to follow it.
If flying VFR with a flight plan, you may request the destination that is auto-populated or you may send “Flying VFR” if maneuvering without a flight plan.
On initial contact with a radar facility, only send one or the other. Checking In and then requesting Flight Following is a warnable offence.
More information on the change can be found here.