This may sound kind of silly and I'm sure any cis woman would know the answer to this.  I have been wearing panties for most of my life.  Some designers of panties  (usually the more expensive ones) feature a small pocket in the front of the gusset.  Over the years I have often wondered just what that pocket is for.  Initially I thought it was a place where one could hide something like money, but that really didn't make sense because it might get wet and smelly.  Then I thought its too small for a pad or a tampon or even a shield.  Bottom line is I still have no idea why it's there.  I know that most of the readers of this thread are not cis women, but I thought that I'd give this delicate topic a try here B4 I ask one of my cis girlfriends.

Hugz!

Uhm, if I've figured out what you are talking about, it's not a pocket.
The extra fabric is just there to make things a little more comfortable and let the area breathe better.
They don't always sew down all the seams, so it might look like a pocket.

For absorbing a little extra moisture before it shows through. I believe that it's called a gusset.

As Harley says, it's for leaks so the outer fabric isn't discoloured - just looks like a pocket but isn't one.