Okay kiddo, so a long time ago, in the year 1791, people in a place called Poland made a really important set of rules called the "Constitution of 3 May". This was like a big list of instructions that everyone in Poland had to follow, kind of like how moms and dads might make a list of "family rules" for everyone to follow.
The Constitution of 3 May said that the king of Poland didn't have as much power as he used to. The king had to follow the rules too, just like everyone else. It also gave people more say in how their country was run. Before, only rich people could vote and make decisions, but now more regular people had a say too.
This was a big deal because it meant that people had more rights and freedoms. It also helped Poland become a more modern country with a fair government. The Constitution of 3 May was really important for Poland and helped shape its future.