Okay kiddo, so a long long time ago, there was a big group of people called the Israelites. They were like a big family, and they all lived in a place called Israel. But one day, something happened and the Israelites got split into two groups- the northern kingdom and the southern kingdom.
Now the northern kingdom was made up of ten of the families from the Israelites, so they were called the Ten Lost Tribes. They were called lost because they disappeared and nobody really knows where they went.
Some people think that they just got lost and wandered off. Others believe that they were taken away as slaves by an enemy army. And some people even think that they went to live in a faraway land that nobody knew about.
Nowadays, there are different groups of people who claim that they are from these ten lost tribes. But nobody knows for sure where they really are or what happened to them. It's kind of like a big mystery that nobody can solve!