Circumcision is surgery to remove the skin at the very tip of the penis.
Baby boys are born with a loose flap of skin that covers and protects the rounded top part of the penis. This skin is called the foreskin. It contains nerves, blood vessels, and a tiny part of muscle.
When you are born, the foreskin is stuck to the penis. It separates as you grow up. This allows urine to better exit the body and lets the skin pull back when you have an erection.