A khanate is like a big boss's own territory. Imagine you have a toy box, and one of your friends is the big boss of the toy box. They can decide what toys everyone gets to play with and what toys they can't play with. They're in charge of everything that happens in the toy box.
In the same way, a khanate is a place where the big boss is called a khan, and they have control over everything that happens there. They decide what people can do, what they can't do, and how things should be run. People who live in the khanate have to listen and do what the khan says, just like how you have to listen to the big boss of the toy box.
Khanates were usually found a long time ago in Central Asia, where different groups of people would have their own khanates. It was a way for the people to have someone to look up to and who could help them in times of need.