Papules are small bumps that appear on your skin and have a rough texture. Papules typically appear on the face, but may appear on other parts of the body. Papules occur when the wall of a hair follicle break and cave in - the visible inflammation is due to white blood cells rushing in.
Pustules are simply the medical term for pimples or zits. They are visible several days after papules have formed, when the white blood cells rise to the surface of the skin. Like cystic acne, pustules can be large and painful. Proper care should be taken to allow the pustule to heal properly.
As acne begins to heal, it will form a red spot on the face with a well defined shape. This is called macule. Macules are not an uncommon site during the healing process, but it will look as if your skin is puffy and inflamed. Macule's are temporary and will disappear by themselves over a few days or even weeks. Picking the macules will also lead to acne scarring and even a new flair up of acne. This should be avoided as well.