The glute kickback is an isolation exercise for the glutes, it works the gluteus maximus main function - extending the leg.
The kickback might also be done with cable or with bodyweight. The bodyweight variation usually won’t allow enough weight to really grow and strengthen the glutes. So that’s where the machine comes in handy.
A machine might be more suitable for beginners, since it puts your body in a more strict form than the cable. The drawback is that a cable will allow more engagement of the core muscles and stabilizers.
An important note, make sure this exercise works your glutes and the lower back doesn’t take part of the pressure. If you feel any pain at the lower back after doing this exercise, don’t ignore it, it might lead to injury. Check if your form is correct, or consider replacing this exercise altogether.
Keep your lower back neutral - Make sure to keep the lower back straight, arching the lower back will move the pressure from the glutes to the back muscles, which wouldn’t be beneficial and might cause back pain.