Installations are mostly CQC assets imported into the main game after many people asked why they weren't in the main game and petitioned FDev to do so. As a result the Galaxy has a lot more places to visit and look at.
You can interact with most of them to some degree (try scanning one), but yeah, not able to interact "normally" by landing/trading with them is a bit of a shame. Even if they would only have "small" landing pads.
Planets occasionally get renamed, for example if someone wins a "name a planet" event, or a significant in-game event occurs. I doubt they were all renamed.. I certainly haven't noticed!
