Blackheads are comedones, which mean they are formed when the skin folds in on itself to make a small pocket, which fills with dead skin cells. The dead cells turn black when exposed to air, which creates the pigment. They are the same as whiteheads, except whiteheads are covered by a thin layer of skin which prevents the dead cells from oxidizing.
Moles are caused by pigmented cells within the normal skin architecture, so they do not have the central umbilication that blackheads have. They can be raised if the pigmented cells grow large enough, and can grow much larger than blackheads. Blackheads are no more than the size of a pinhead, but moles can be several inches in diameter.
Moles can only be removed surgically, but blackheads and other comedones go away when treated with topical retinoids, which are available both over the counter and in prescription strength (Retin-A).
If you have further questions about your skin, you should make an appointment to discuss them with your doctor
. If a pigmented spot starts to grow, change, or bleed, it should be evaluated immediately by a physician to rule out melanoma, which is a very aggressive form of skin cancer.