Pullovers work a lot of muscles: back, chest, shoulders, triceps, even the abs somewhat as you stablize the core when you pull back. Whether the focus is on the back or chest depends somewhat on your mental focus. I find that if I concentrate on the top 30 percent or so of the move, I can feel it more in my chest. If I concentrate on the lats in the bottom 30 percent of the move, I feel it in the lats (especially if I kind of press my scapulae into the bench on the lift). One of my reference books shows the pullover in both the chest and back section. In the chest section, you are lying with upper back supported on a bench (crosswise) and hips down. In the back section, you are in the same position, but with hips up.