Here are a few explanations:
Epidermal stem cells are found in the basal layer of the epidermis. It is responsible for the regeneration of the different layers of the epidermis.
Hair follicle stem cells are needed for the renewal of the hair follicle. They also play a role in regenerating the epidermis and sebaceous glands when the tissue is damaged.
Melanocyte stem cells are responsible for the regeneration of melanocyte, which is a type of pigment cell. These cells allow the production of the melanin production that gives the skin pigmentation.
Skin Regeneration 