A birthmark is a colored mark on the skin that is present at birth or appears shortly after. These marks can vary in size, shape, and color, and they are usually harmless. Birthmarks can be classified into two main types: vascular birthmarks, which are made up of blood vessels, and pigmented birthmarks, which contain clusters of pigment cells. Most birthmarks do not require treatment and may fade over time. However, some may need medical attention if they change in appearance or cause discomfort. Common types of birthmarks include strawberry hemangiomas and moles.