Final answer:
A birthmark or congenital mole caused by the dilation of small blood vessels is known as a vascular birthmark, such as a port-wine stain or strawberry hemangioma.
Step-by-step explanation:
The name for a birthmark or congenital mole caused by the dilation of the small blood vessels is a vascular birthmark. This type of birthmark can be seen in various forms, such as a flat pink, red, or purple mark known as a port-wine stain, or a raised, bright red birthmark known as a strawberry hemangioma. These marks are generally harmless but can sometimes be associated with underlying health conditions. The dilation of blood vessels leading to such marks can also be seen in cases of idiopathic juxtafoveal retinal telangiectasia and petechiae, which occur due to blood leaking out of damaged vessels.