Hyperpigmentation is a broad umbrella term that refers to different forms of discoloration in the skin. Post-inflammatory hyperpigmentation (PIH) is a type of hyperpigmentation caused by acne. With PIH, a small area of the skin where a pimple has healed is left discolored (although the texture of the skin doesn’t change).  Many people use the term acne scars to describe PIH. However, acne scars more accurately refer to raised or pitted scars left behind after a blemish heals. These types of scars are harder to treat than PIH.