Nuit debout is an event in France where people come together to talk and share their opinions about how things are going in their country. They usually meet at night and stay up really late (hence the name "nuit" which means "night" in French). They talk about things like politics, the economy, and social issues.
Imagine you and your friends staying up all night and having a big sleepover party. But instead of playing games or watching movies, you all sit in a circle and talk about things that you think are important. Some people may talk about things they like or dislike about the school they go to, while others might talk about things they wish their parents would let them do.
That's what nuit debout is like, except it's not just for kids and their friends. It's for everyone in France who wants to talk about what's happening in their country and how they can make things better. It's a way for people to come together and share their ideas and opinions, just like you do with your friends.