"Infinite" 2D tiles, like many *many* other games.
Terrain chunks that impede travel -- you can go through them but it takes real time to move around. I'm thinking swamps or whatever. These aren't single tiles, they're groups that get generated in some sculpted wilds-like way. Going around them is usually better (particularly with a map). They do also serve a purpose with a Shovel, which will also slowly clear them.
A little bit different in the descriptions here is that you can see tiles further away than just your adjacents. These give you a vague direction and distance, and also update your map, which is probably quite important with this game. Occasional Watchtowers have broken ladder segments you have to repair and will do something similar on a bigger scale (particularly useful for finding other Watchtowers).
The actual useful tiles are limited in number:
Terrain chunks, as mentioned.
Watchtowers, as mentioned.
Ponds
Individual Trees.
Cave entrances.
Towns.
These all spawn randomly.
Regions are squares of some size surrounded on all four sides by Mountains. More on that in that section. Regions constrain the resources that are found within. Mountains will also modify POIs that appear on their tiles.
