A presser foot holds the fabric while you sew on your sewing machine. Under the presser foot and fabric are feed dogs that move the fabric through your machine. On most machines, the presser foot can be changes to best fit the sewing job. For example, a zipper foot allows you to sew close to the teeth on the zipper. A walking foot helps keep fabric in place when sewing through multiple layers of fabric.
In this photo, the walking foot is on the left side in the back. In the front is a darning foot. The foot with #37 is a ¼ inch foot. The foot on the right is an all purpose foot.