Okay kiddo, let's talk about the Treaty of Nerchinsk!
Imagine two kids playing with toys on the playground. One kid has a toy that the other kid really wants, but they keep arguing and fighting over it. Eventually, the teacher steps in and makes them share the toy, so they can both have a turn playing with it. That's kind of like what happened with the Treaty of Nerchinsk.
In the olden days, there were two big countries called Russia and China, and they both wanted control over a piece of land called Siberia. They started fighting over it, but they both realized that it was causing a lot of problems and they weren't getting anywhere. So, they decided to make a treaty (like an agreement) to share the land and make peace.
The Treaty of Nerchinsk was signed in 1689, and it was the first treaty ever signed between Russia and China. It said that Russia could have the land to the north of the Amur River, and China could have the land to the south of it. They both promised to stay on their own side and not fight over the land anymore.
Now, you might be wondering why they called it the Treaty of Nerchinsk. Well, Nerchinsk was a town in Siberia that was right near where the treaty was signed. It's kind of like when you sign a paper at school, you put the date and your name at the top, so you know when and where you signed it.
So, that's the Treaty of Nerchinsk in a nutshell! It was a way for Russia and China to stop fighting over a piece of land and share it peacefully.