Okay kiddo, so you know how our country has different states, right? Well, a long time ago, there were two territories, Kansas and Nebraska, that wanted to become states. But there was a problem - people couldn't agree on whether or not they should allow slavery in those states.
Some people thought slavery was wrong and didn't want it to be allowed in any new states. Other people thought it was fine and should be allowed. This disagreement caused a lot of arguments and fights between people in different parts of the country.
The government decided to solve this problem by creating a law called the Kansas-Nebraska Act. This law said that the people who lived in those territories should be allowed to vote on whether or not they wanted slavery in their state.
This might seem fair, but it actually caused even more trouble. People from all over the country started moving to Kansas just so they could try to get their side to win the vote. They sometimes even cheated by voting multiple times or using weapons to intimidate others.
This led to a lot of violence and fighting between different groups of people. The Kansas-Nebraska Act didn't solve the problem of slavery in new states, it just made things worse for a while. Eventually, the Civil War happened and slavery was abolished everywhere in the United States.