The chin-up is a bodyweight exercise that targets the muscles of the back, including the lats, traps, and biceps. It is typically performed using a bar or other stable surface that is set at about chest height.

 To perform the exercise, you will need to grip the bar with an underhand grip, palms facing toward you, and hang from it with your body straight and your heels on the ground. From there, you will need to pull your chest up toward the bar, squeezing your shoulder blades together as you do so. Be sure to keep your body straight and avoid swinging or using momentum to lift your body. 

It's also important to use a grip that is challenging but manageable and to avoid rounding your back or arching your lower back during the exercise.