I'd try to explain this myself, but first of all I'm pretty new to sock knitting myself and secondly, there is an excellent description of the process in Silver's Sock Tutorial
(start of the tutorial). The gusset
, which is the part you are on now is explained here
I'm just knitting my first pair of socks, too, and I'm following Silver's tutorial. It rocks! I'm just done with the gusset myself and am knitting towards the toes on the first sock now...
Good luck and let us know how it's going!