Tile
A tile is a 4 meter by 4 meter square on the ground, which pretty much makes up the world of Wurm.
A tile can be dirt (packed dirt or cultivated, farm field, etc), grass, sand, clay, rock, road (cobblestone, gravel, slab, wooden planks), mycelium, peat, tar, tundra, moss, marsh, cliff, steppe, lava, or water.