Pull-ups works your latissimus dorsi. Infact its one of the best exercise to train your back!
I can perform 15 pull-ups at a time, and also use a weighed belt.
However, I was not strong many years back. Just like many gym goers, I wasn’t able to do even a single pull-up!
There are two alternative’s to pull-ups until you get strong enough to pull your own body weight:
1. Lat pulldown Machine
2. Assisted Pull-up Machine
3. Band Assisted Pull-ups (in case you don’t have the assisted machine in your gym)
Hope this helps:)