Lunges are an extremely effective exercise for overall leg development and basically involve giant steps in the exercise movement. Lunges can be performed either with a barbell behind the neck or with dumbbells placed in each hands. For beginners I recommend using dumbbells as they are much easier to control during the movement.
Lunges primarily target the hamstrings, quads, glutes, and lower back. Secondarily, just like squats this exercise uses almost all other muscles in the body.
To perform lunges stand up straight with a dumbbell in each hand hanging down by your side. Your feet should be shoulder width apart or just a little less. With either leg take a big step forward and bend at the knee until the front thigh is parallel with the ground. Your rear leg should be bent at the knee and balanced on your toes. Step back to your starting position and repeat the motion with the other leg. Alternate legs until you have completed the desired amount of repetitions.