The squat is a lower body exercise that targets the muscles in the upper leg and lower back. It develops general lower body strength, and it develops stabilizing muscles around the hips, abs, and lower back.
When watching the following video, break the movement down into four segments: Stance, Descent, Ascent.
Each squat variation places the barbell at a different resting point. The variations put strain in different stabilizing muscles, though the primary muscles involved remain the same.
The front squat changes the Stance and Bottom segments of the movement. It places more strain on the quadriceps and abs. The bar is positioned on the front shoulders with raised arms, and the back is more upright. At the Bottom, the knees are pressed forward and the shins make a sharper angle with the ground compared to the Back Squat.
The pause squat is identical to the back squat in movement. The difference is that when you reach the bottom, the position is held for three seconds.