Lentigo is a small, flat, brown spot on the skin that is usually caused by sun exposure. These spots are often referred to as "sun spots" or "age spots" and can appear on areas of the skin that have been frequently exposed to sunlight, such as the face, hands, and arms. Lentigines are generally harmless and do not require treatment unless they change in appearance. There are different types of lentigo, including lentigo simplex, which is typically present at birth, and solar lentigo, which develops over time due to UV exposure. While they are common in older adults, lentigines can occur in people of all ages. Regular skin checks are recommended to monitor any changes.