Works: Glutes, quadriceps, and hamstrings. (Also calves, lower back, upper back, and abdominals).
With the barbell resting on the back of the shoulder and your hands in a wide grip, lower as if about to sit down. Make sure toes are slightly pointed outward and that your knees don’t go over your toes as you go down. You can also do this exercise at a squat rack, which is best if you’re barely starting, as the bar is on a rail and will guide you up and down, helping you achieve good form from the very beginning.
Start with lower weight until you master good form and then add more weight as you get stronger. Try different speeds to really challenge your legs! Slow is always best, though.