What is the difference between the entries highlighted in green as opposed to those in plain black. Do those highlighted entries present what my Pi is actually receiving, or am I receiving both and only the green entries have the ADS-B system?
Highlighted is ADS-B (with positions), the others do not have positions.
So the others that do not have positions, are they a system other than ADS-B?
Yes, those are from Mode S transponders. Mode S only sends altitude data, as opposed to ADS-B which sends full position data. Mode S is older technology, which means that it’s very widely adopted. ADS-B, on the other hand, is relatively new.