In the earlier chapters Sun Tzu spoke of how to camp and how to observe the enemy. Now he moves to how the ground underfoot itself changes a fight.
The same army wins or loses depending on the ground it stands on. So Sun Tzu divided battleground into six kinds.
地形有通者，有掛者，有支者，有隘者，有險者，有遠者
di xing you tong zhe, you gua zhe, you zhi zhe, you ai zhe, you xian zhe, you yuan zhe
Ground comes in six kinds. Open, entangling, standoff, narrow, steep and distant. (The Art of War, Terrain, translated directly)