The back and biceps are the primary muscles in any pulling movement. The pulling movement consists of pulling a resistance or load towards your body. Or, in the case of the pull up, the "King" of back exercises, you pull your body towards a fixed point.
You can perform a vertical pulling motion that is parallel to the body.
- pull up, chin up, or seated cable lat pull down (various grips)
You can also perform a horizontal pulling motion that is perpendicular to the body.
- bent-over dumbbell/barbell row, inverted barbell row, and resistance band row
As previously stated, the pull up/chin up is "King" for targeting the back AND the abdominals. However, assisted pull up machines can be used until strength gains permit attacking the good 'ole pull up.
An exception to my "no machines" rule is the seated cable lat pull down. Despite the fact that you're seated, decreasing recruitment of the abs and glutes, you must still stabilize your trunk muscles and hold a tight posture to perform the movement. Plus, it can help you get to the point of true pull ups/chin ups.
Make it a great day!