With circumcision the skin that covers the glans is surgically removed. This normally is done shortly after a child is born.
Without foreskin the glans is permanently exposed, making circumcised penises look different from uncut ones.
Circumcision becomes more complicated and riskier in infants older than two months, in boys and men.
Today most people hold the view that the benefits of circumcision are not significant enough to recommend circumcision at birth.

I’m seventeen and want to be circumcised. Do I need permission from my parents?
Where can my friend go to get circumcised?
I’m embarrassed because I am the only one of my friends without a foreskin.
Is sex different for men who are circumcised?
I am circumcised but want my foreskin back. Is there any way to do this?