Retinol is the primary form of Vitamin A. It is a nutrient essential in growth, repoductive, and vision processes. In skincare, it's used for its cell communicating and antioxidant properties.
Prescription retinol (aka: tretinoin, retinoic acid or all trans retinoic acid, brand names vary) penetrates the skin's outer-most layer into the deeper dermal area, aiding in healthier cell formation. This means a reduction in hyper-pigmentation (age/sun spots), acne and psoriasis. Retinol also stimulates collagen production, which means fewer wrinkles. At high-levels, retinol can actually help to protect from the development of skin cancer.
Keep in mind, over-the-counter retinol is not regulated and may not have the same effect as the prescription forms.
Because retinol works to expose new skin, users will be more sensitive to the damaging effects of the sun. Use of a daily sunscreen is an imperative part of any routine that includes retinol.