It has two pockets, with openings on the sides. Inside the right pocket is another pocket, with the opeining on top. On the inside of this pocket, (i.e the side closest to the wearer) there is a hole, that is there on purpose (stitching around the hole) It is roughly teardropped shaped (point upwards)
Those all sound like solid guesses. I’d add something like ski lift passes on a cord, or a keychain that won’t let go when you’re tumbling down a hill.
In my father’s day, suit trousers often had an inner pocket just right to hold a Zippo lighter. Time brings change.