One thing is certain, knowing how to tie knots is a must for rock climbers. Some knots serve many purposes, many knots serve one purpose, but not all knots serve all purposes. In other words, there are many different knots that serve many different purposes.
Outdoor has provided us with a few basic climbing knots:
Retrace Figure Eight
The retrace figure eight is the most secure and efficient way to connect the end of a rope to a climbing harness.
https://www.youtube.com/watch?v=aLopeVBb7yU
Girth Hitch
The girth hitch is essentially what you do with a luggage tag. It’s useful for attaching slings to various things, like the two hard points in a harness—or when slinging a tree for protection.
Clove Hitch
The clove hitch is useful for attaching a rope onto a carabiner, or tying in at an anchor. https://youtu.be/pwdZTHu5rTI