The squat is one of the best movements the human body can do. Squatting helps keep the muscles and nerves of the pelvic floor healthy, decreases compression forces on the lumbar and thoracic vertebrae, helps with thoracic expansion upon inhalation and helps diaphragmatic movement to name a few.
Next time you are around a child or children watch them move around, watch them squat, they will do it effortlessly and hang out in the squat position as they play. As we get older and become more mobile on our feet and walk around more we tend to lose the ability to squat low. The ability is lost because we do not intentionally put ourselves in that position and start sitting in chairs, muscles become tight and the ability for hips, spine and legs to move together disappear. This can then cause the issue of squat limitations when people go to workout and squat and cannot get into a deep squat position.
What we look for in the squat is the ability to maximally squat down hips to heels keeping the heels flat on the floor and the center of gravity over the heels. If there is an inability to get into that position it can be due to tight and over toned back extensors, inability of the abs to create position with the ribcage for correct hip movement, or incorrect position of either left and right hips.
Try it at home! Stand up in front of a chair with your feet about shoulder width apart. Engage your glutes to stabilize your hips and use your ankle mobility by guiding your knees forward over your toes and when you feel your butt hit the chair, push the floor away and contract your glutes.
Do a set of 10 reps then try to find something lower than a chair. Not everyone can get proper depth in a squat but you want to comfortably be able to drop low enough so that your femur is parallel to the floor, doing so in a way where your shins are parallel to your spine.
Do 2 more sets of 10 reps, working to your lowest depth and take note of where you feel the tension.