When we think of an acne scar, it's like a dent in the skin like a chicken pox mark. This is caused by severe cystic acne and when that heals a lot of the time it forms that deep scar. A post-acne mark is really totally different -- the skin is still smooth. But what's happened is that the inflammation of the acne causes the inflammatory response which causes your melanocytes, the cells that produce pigment, to be appearing there. So think of a post acne mark the way you would think of a sunburn. You get a sunburn with inflammation and then you get a tan, but that's all over your whole face. But in this case it just happens where you have the pimple.