The Wall Press Abs exercise is an excellent way to learn how to create protective stiffness in the spine. When performed correctly it will help create stability through your low back and aid in creating increased mobility through your hips. Being able to dissociate between the low back and hips/pelvis is a region where many people with hip or back pain struggle.
By pressing your arms into the wall you will help engage your abs. Holding this position, then taking a breath in then exhaling and allowing your ribs to drop down will activate you oblique muscles further. Then maintaining this position of ribs down inhaling and exhaling will incorporate your diaphragm which is a muscle and spinal stabilizer as well.
Finally you will begin to move or extend your legs out which will continue to challenge core control while you work hip mobility. Below are the progressions from easiest to most advanced.