Adjusting brake pads
The brake pads on this kind of brake (V-brake) are adjusted with the screw above the one you've circled. The screw at the end of the pad adjust the positioning of the pad relative to the rim. It's one of the jobs where you ideally need 4 to 6 hands to get it right.
The screw that you circled adjusts the symmetry of the pull, or the timing of the pads touching the rim by adjusting the tension of the springs in the pivots.