The squat is arguably the king of all exercises. Few movements are as effective at strengthening the body and as functionally important as the squat. If you doubt my last statement, try getting out of your chair right now without a squatting movement.
Almost every lower body exercise worth its effort is in some way a variation of the squat. Lunges, step-ups, deadlifts, single-leg squats, etc. all follow the same body mechanics of hip and knee flexion and extension. However, like most high-value exercises, squatting comes with its fair share of injury risk, especially to the knee. This fact is even more true if you are a female.