Dr Bob
The area just under the penis head is the frenulum prepuci or the point where the foreskin (the prepuce) was attached before circumcision. It is just below the little 'v' formed by the corona or the ridge which borders the head.
It is the main nerve centre for the penis, exceeding the sensitivity of the head or the shaft. Often, simple rubbing of this area is enough to provoke orgasm.
Removal of the foreskin in circumcision is, as has been said, sometimes a religious issue and sometimes a medical necessity. I am not going to get into the issue of the rights or wrongs of elective circumcision.
One significant benefit that I have noted from circumcision is that the exposed head is less ultra sensitive than that shiny area exposed by pulling back the foreskin of an uncut man. Thus, it seems, circumcised men are less prone to premature ejaculation. perhaps there needs to be a study on this. I base my statement on examining many men, both cut and uncut.
For my part I can barely remember being circumcised. I guess I was about 4 when Dr Spencer and his brother, also a doctor arrived at the house. Without any ceremony, explanation or by your leave I was placed naked on our scrubbed kitchen table, a cotton gauze mask put over my face and a substance I now recognise as ether, poured on it.
I knew nothing till I awoke with a sore bandaged penis but I was mighty embarrassed when a week later I had to go and display the handiwork to the doctor and have the single stitch out.
At 71 I guess I'm reasonably qualified to attest that the experience did me no harm and that I must have gained many hours of wonderful sex by not being so trigger happy.