Skin glands are specialized structures in the skin that produce and secrete various substances. The two main types of skin glands are sebaceous glands and sweat glands. Sebaceous glands produce an oily substance called sebum, which helps to keep the skin moisturized and protects it from bacteria. Sweat glands are responsible for producing sweat, which helps regulate body temperature through evaporation. There are two types of sweat glands: eccrine glands, which are found all over the body and help cool the skin, and apocrine glands, which are located in specific areas and become active during puberty.