Stephanie asked me something the other day that, quite frankly, I couldn't even begin to answer. What is the little hole for in men's underwear? It's in every pair of briefs I own, ditto for pajama pants.
The sad truth is I have absolutely no idea. One would think it would be used to to pee through, but fishing out Little Jeffy through that hole is a bitch, especially if it's cold. It's much easier and faster to just pull your pants down.
I remember trying it once when I first had "big boy" underwear. Seemed like a lot of work at the time so I never did it again. Now that I'm older and wiser, I'd speculate it's like the Ron Jeremy escape hatch or something. Instead of pitching a tent you deploy the probe.
No one may really know.