Whats the extra foreskin in my ?

I am totally happy with my 6 inch( maybe even smaller) , no need for anything. I masturbate several times a week, and ain't afraid to admit it. I clean my everyday, and do my monthly testicular self exams. But I'm curious, why do I have excess foreskin at the tip of my . It goes away when in erect state. Its only like half a centimeter long. Is this actually a benefit?