Melanocytic nevus refers to common moles on the skin composed of nests of altered melanocytes.  Junctional nevi have nests of nevus cells only at the dermal-epidermal junction. Intradermal nevi are the most common type in adults and are confined to the dermis.
Compound nevi contain nevus cells at the junction and in the dermis. Congenital nevi appear at birth or within the first six months of life as small, flat, lightly pigmented lesions whereas acquired nevi develop later in life where sunlight exposure is the major risk factor for their development and there is a very small risk of malignant transformation. Surgical removal  is indicated primarily for cosmetic concerns or for worrisome changes in size, color, or elevation.