The machine high row, also known as leverage high row is a great exercise for your upper back. It primarily targets the large latissimus dorsi (known as the lats) which is the muscle that spans much of the upper back. And it also works the rhomboids and the teres major. The shoulders and biceps assist as secondary muscles.
The high row is a unique back exercise, because most back pulling exercises allow you either pull vertically like with chin ups and cable lat pulldowns, or horizontally, like with bent-over rows and seated rows. But the high row is somewhere in middle. This allows you to hit your back muscles in a whole different way, combining these two movements together.
Some high row machines are isolateral, which means each arm is moving on its own, the benefit of isolateral machines is that they allow you to fix strength imbalances, because the strong side cannot compensate for the other.
The high row can be performed with a machine or with a cable. Doing this exercise with a machine is usually easier for beginners, since the machine keeps your body supported. While the cable version will allow you free movement and require more stabilization work.
Adjust the handles so that when your arms are straight the weight stacks are a little lifted, so there is a constant pressure on your muscles.
Focus on your back muscles. You should move the upper arms with your lats, don't turn it into a bicep curl. Think of your arm as merely a hook to connect the resistance to your lats and mid-back muscles.
Do this exercise in a slow and controlled manner. Return the handles back slowly, don't just let them drop back up. This will put more pressure on your muscles and will help you to avoid from using momentum.