Alright kiddo, so imagine you have a really big playground, and you're the leader of it. You have a lot of friends who come to play with you, but there are some bullies who come from another playground and try to take over yours.
Now, you're strong and brave, but you can't handle all the bullies alone. So you make a deal with your older brother, who is much stronger and has a lot of friends too. You ask him to come and help you protect your playground, and he agrees.
But he doesn't do it for free, of course. He says that he will help you, but in return, you have to listen to him and do what he says. He becomes a sort of protector over your playground, making sure that bullies don't come and mess things up.
This is kind of what happened with Imperial China and the countries it protected. China was the big kid on the playground, and there were smaller countries and peoples who lived around it who were constantly being threatened by other, stronger countries.
So China made deals with these smaller countries, saying that they would protect them from invaders or bullies, but in return, these smaller countries had to listen to China and follow China's rules. These smaller countries became protectorates of China, meaning that they were under China's protection and influence.
Just like in our playground example, sometimes these protectorates didn't always like following China's rules and wanted to do things their own way. But because China was so strong, they had to listen or face the consequences.
Does that make sense, kiddo?