Comedones are a type of acne lesion that form when hair follicles become clogged with oil, dead skin cells, and bacteria. They can appear as open comedones, commonly known as blackheads, or closed comedones, known as whiteheads. Open comedones have a dark surface due to oxidation, while closed comedones remain under the skin's surface. These lesions are often associated with conditions like acne vulgaris and can occur on various parts of the body, including the face, back, and shoulders. Proper skincare and treatments, such as topical retinoids, can help prevent and reduce the appearance of comedones.