Okay kiddo, listen up! A long time ago, in 1905, the French government decided that they were going to separate the churches and the state. That means that the government and the churches were going to be separate from each other.
Before this law was made, the government and the churches were very much connected. Churches were able to do some things that the government would normally do, like providing education and taking care of the poor. But the government thought that it wasn't fair to have one specific religion in charge of these things.
So, they made the law that said that the government and the churches had to be separate. This meant that the churches could still exist and people could practice religion, but the government couldn't do anything to favor one religion over the others.
This was a big change for the people in France because they were used to having the churches very involved in their daily lives. But, over time, they got used to it and now it's just normal for the government and the churches to be separate.
Remember, it's important to respect everyone's beliefs, even if they're different from our own.