Damaging Terrain

This is Terrain that causes damage to a creature (the amount and type of damage specified by the specific terrain). Lava Fields, Acid pools, Pyroclastic Flow, are all examples of damaging terrain.

Damaging Terrain applies its damage immediately when a creature enters the terrain, and then once per round thereafter. Leaving the terrain prevents further damage. A creature can take damage from the terrain at most once per round, even if they leave and reenter repeatedly in the same round.

Hobbling Terrain

Hobbling Terrain is a special kind of damaging terrain, where damage is only incurred while moving in the terrain. Such terrain deals its damage for every 5ft of movement taken through it.

Overland Travel

Its only possible to move overland through Damaging Terrain when you are completely protected from it (or have mitigated the recurring damage in some way). Otherwise the terrain will kill you before you make any significant headway.