Vascular birthmarks are skin markings that occur due to abnormal blood vessels in the skin. They can appear as red, purple, or blue spots and vary in size and shape. Common types include hemangiomas, which often develop shortly after birth and may fade over time, and port-wine stains, which are usually permanent and can darken with age. These birthmarks are generally harmless and do not cause health problems. However, some may require treatment for cosmetic reasons or if they affect vision or other functions. Treatments can include laser therapy or other medical interventions to reduce their appearance.