What show size shoe do the sizes correspond with?

I wear size 5 1/2 and the small are still a tad bigger than I'd like, so I bet medium would fit you fine. BTW, even though they're not as snug as I'd like, I still love them and have bought several pairs.

how many socks in a pack?

Three pair. They're great socks. I ordered a few different sets. These have the right amount of cushioning in the right spots.

I am confused about the sizing of these socks. i wear a size women's 11 shoe (regular, not wide) would the large or the extra large be the correct fit

Depends on how tight a fit you like. For me (also a size 11), I prefer XL. XL is much more comfortable, for just casual wear. But if you're talking about "during exercise", or "working on your feet, all day long", then you'll want just the LARGE, because of a feeling of more foot support, than the larger sock.

are these men's or women's socks?

Both - They're unisex and they fit great! (more comfortable for women; however, or even men with smaller feet. Otherwise, you'll feel a nice stretch, but the great news is that they will retain their stretch-and-bounce-back feel, for a long long time. Therefore a great athletic sock, that you don't have to constantly pull-up...)