Okay kiddo, so have you ever heard of Jeju Island? It's in South Korea, and it's a really pretty place where lots of people like to go on vacation. But a long time ago, in 1948, something really bad happened there. There was something called an "uprising," which means a lot of people started fighting because they were really unhappy about something.
The people who were upset were called "leftists," which means they wanted things to be more equal for everyone. They were mostly farmers and poor people who didn't have a lot of money or power. They didn't like the government that was in charge of Jeju Island at the time, because they thought the government only cared about rich people and didn't care about the poor people.
So the leftists started to protest, which means they all got together and said things like "we want things to be fair for everyone!" But the government didn't like this, so they sent the army to stop them. The army was really mean and they started shooting at the protesters, even though they weren't doing anything wrong.
This made the leftists really angry, so some of them started fighting back. They attacked the army, and the army attacked back. It was really scary and a lot of people were hurt or killed. Some people even had to hide in the mountains to avoid getting hurt.
This fighting went on for several years, and it was really sad because a lot of innocent people got hurt. Finally, in 1954, the government stopped fighting and they made a peace agreement with the leftists. But by then, a lot of people had already died or had to leave their homes.
So that's what happened during the Jeju Uprising. It was a really sad time in history, and we should always remember it so that we can work to make sure something like that never happens again.