Okay kiddo, so Cuba and the United States used to be really good friends a long time ago, but something happened and they stopped being friends. In the 1960s, a man named Fidel Castro took control of Cuba and made some changes that the United States didn't like. The U.S. put some rules in place that made it hard for people to travel to Cuba and for businesses to work there.
For many years, the U.S. didn't want to be friends with Cuba because they thought Cuba wasn't treating its people very fairly. But a lot of other countries still talked to Cuba and did business with them. In recent years, some people in the U.S. started thinking that it might be a good idea for the two countries to start talking again.
So in 2015, the U.S. and Cuba decided to start talking and working towards being friends again. They made some new rules that made it easier for some people and businesses to work in Cuba, and for some Cubans to visit the U.S.
But some people don't think it's a good idea to be friends with Cuba again, and some people in Cuba don't trust the United States. It's like when you have a fight with one of your friends and it takes a while to be friends again - sometimes it's hard to forget the things that made you fight in the first place.
So right now, the two countries are still kind of figuring things out, but they've made some progress towards being friends again.