It's also in ability descriptions, like Maya's Skies of Itzamna (The Palace gains Science for adjacent Vegetated tiles.)
From what I've seen and what JNR and others have put together, it seems like "Vegetated" is the catch-all for "dry" features.
The ones that I can name so far are:
Rainforest (vegetated Plains; maybe Tropical too?)
Woods (vegetated Grass; maybe Tundra too?)
Sagebrush (vegetated Desert)
There is also a "Wet" feature category. I do not believe "Rivers" belong to this category. Rivers seem to always be called out as their own thing. The "Wet" features spotted so far are:
Watering Hole (Plains)
Marsh (Grass)
Swamp (Tropical)
Oasis (Desert)
I'm not sure where coastal features fit in. (We've spotted reefs, or something that looks like them at least)
Overall, my take on this categorization is that it's a great reflection of the streamlining philosophy of Civ 7. It will make it easier to apply and figure out feature-based bonuses, like in Maya's ability.