What happens in 'civilized' systems? You can honk there, and use FSS. You can also use DSS. But you will not be able to sell the data, because such system have a Nav Beacon, and you can get all the data scanning it. Sometimes - in systems with a Nav Beacon - the entire result of the FSS scan pops up, this seems to happen, when you are near the Nav Beacon, so you do not need to drop out of SC and scan it. You need to scan it anyway for missions, even if you know the system already.
There are two different kinds of "civilized" or "inhabited" systems. You used to be able to easily tell them apart on the galaxy map, but you can't any more.
Systems with over 1 million population (as a general rule) are "pre-Explored". When you arrive in the system for the first time, you get all the data for all the planets instantly available to you on the radar and system map. Honking or using the FSS does nothing in such systems except discover the ephemeral POIs (all the planets will be pre-scanned for you). Since there is no FSS or honk data, you cannot sell such data from systems like these. You can, however, still map them, and if you're lucky enough to find planets that no-one else has Mapped yet (there are still a few about the place) you can claim the "First Mapped By" Tags. Note that the three Superpower capital systems (Sol, Achenar, Alioth) are considered "pre-Mapped"; you cannot map these worlds or claim credits for probing them.
Systems with less than 1 million population, including uninhabited systems, are almost always considered "Unexplored". When you arrive in such a system for the first time, you get the passive scan of the primary star and anything else within passive scan range (about 30 Ls), which will often include asteroid clusters and any Metal-rich planets in close orbit around the star. When you honk, you get all the data on any other stars in the system. You then need to use the FSS to find all the moons and planets in the system, as well as any more remote asteroid clusters. You can sell this passive scan data, honk data, and the FSS data, you obtain for any planets you scan. You can also probe and map the planets to get mapping credit (and First Mapped tags, if no-one else has ever done so), just like in a pre-Explored system.
There are essentially three different sub-varieties of "Unexplored" systems:
1. Systems which other CMDRs have fully explored before you (using either the FSS or the old pre-3.3 fly-up-and-wait surface scanning method). When you Honk in such systems, you get all the planets revealed to you on the radar and system map, though they are labelled as "Unexplored" on the system map until you run the FSS (or fly into passive scan range). Pretty much every Unexplored system within 500 LYs of Sol, and many of the systems along the popular tourist routes, are going to be this type.
2. Systems which other CMDRs have only partially explored. With the FSS, a "partially explored" system is less likely to occur, since exploring an entire system is relatively quick and effortless compared to the old pre-3.3 method, but you will still find plenty of "legacy" systems where pre-3.3 players have only partially scanned a system. When you Honk in such systems, you only get the planets revealed to you that have been previously scanned and Tagged by others; Untagged planets will be invisible to you, both on the radar and on the System map (though you can infer their existence if there are "strange gaps" in the system map, like a Planet 3 and Planet 5 visible, but Planet 4 is missing). Once you get out around 1000-2000 LYs , this kind of system becomes commonplace.
3. Systems which no other CMDR has ever visited, or at least has never sold the data for. When you Honk in such systems, all you see on the radar and system map are the stars (and any planets within passive scan range) - you will have to use the FSS to find every other planet and asteroid belt. You've got to get out beyond about 2000 LYs or so before you start to see these.
