Most people are to internally rotated at the shoulder. Over the long run, this can lead to compromise at the rotator cuff and problems with balancing the movement of the scapulae. The face pull is an exercise that targets the external rotators (teres minor, infraspinatus), as well as the lower trapezius. This will help promote an upward rotation of the scapulae. A very good thing. I think the biggest benefit is that it helps bring about structural balance. A topic I will talk about more later. Basically your internal rotators tend to be 25-35% stronger then your external rotators. So a little extra work on those ER goes a long way.
Stand in front of a cable machine with the cable coming at face level. Attach a tricep rope handle. Step away so that your arms are fully extended towards the cable machine. Keeping a neutral grip (thumbs up), pull the cable towards your face. You should end with the the shoulder blades fully retracted and the forearms faceing the ceiling.
Always look to maximize your time in the gym. So a good pairing would be to do this exercise and immediately stretch the pecs and lats. Both big internal rotatores. Try doing 4 sets of 12 a few times a week and you will be well on your way to being more balanced throughout the shoulder girdle.