Hook grip, why, How to do?

In this video, we have a time to know a principal of hook grip, why hook grip is applied at the weight lift and how to use a hook grip.
Actually, I also feel pain when I use a hook grip, however, it has a great difference between using a hook grip and not.
Weight lift is hook grip! Next video I will let you know that how to reduce a pain when you use a hook grip.