Live view data source - highlighted green vs black entries

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.