A birthmark is a permanent spot on your skin, often dark brown colored. The actress Marilyn Monroe was famous for a small birthmark just above her lip.
Most birthmarks are present from birth or soon after, and many are pigmented much darker than the surrounding skin. Strawberry and port wine birthmarks, on the other hand, are bright red. The causes of birthmarks vary, but they're almost always harmless. In the 17th century, they were sometimes called "longing marks," supposedly demonstrating the pregnant mother's longing for something before her baby was born.