What is the difference between vasoconstriction and vasodilation?

Vasoconstriction is when blood vessels are narrowed through the contraction of pre-capillary sphincters, whereas vasodilation is when blood vessels are widened through relaxation of the pre -capillary sphincters

Vasoconstriction is the narrowing of blood vessels and happens to blood vessels in the skin when a person is cold to conserve heat energy.

Vasodilation is the widening of blood vessels and happens to blood vessels in the skin when a person is hot to allow heat energy to be lost.