The foreskin is a flap of skin that covers the glans, or head, of the penis. The purpose of this flap of skin is believed to be twofold. First, it protects the glans both in utero and after birth. It is also packed with sensitive nerve endings which can add to the pleasure a man experiences during foreplay and sex.
More About Foreskin
All men are born with foreskin, but it has become a common practice to remove it shortly after birth in a surgical procedure known as a circumcision. It is believed that the removal of the foreskin was first started as a religious practice or rite of passage. Today, this practice continues for hygienic and aesthetic reasons. However, because circumcision isn't medically necessary, it has been falling out of favor in recent years.