How to use help?

During this task I tried in my console help(sort) and that works fine giving me options of what I can use inside sort. By how can I access what is a possible list of thing being used with key. I tried help(key.sort) but that lead nowhere.

Any advice or general tutorial on how to use help? The idea is that I would like to use it in a way that will let me be more independent in solving my problems. Rather than having to look for solutions other people found I could solve problems myself as that's how I learn quicker.