The foreskin (prepuce) is a protective hood covering the glans, keeping it moist.
·        It’s double-layered with skin outside and mucous membrane inside.
·        With masturbation and intercourse the foreskin normally glides back and forth over the glans, stimulating the head indirectly.
·        When the penis gets erect, the foreskin rolls back on itself, uncovering the glans.
·        The elastic tissue at the interface between the inner and outer foreskin is called the ridged band.
·        If a guy becomes circumcised his foreskin is removed. Because the glans is constantly exposed it dries out and becomes less sensitive.

See also: tight foreskin, phimosis and circumcision