The Schuman Declaration is like a big, important piece of paper that was written a long time ago by a man named Robert Schuman. He wanted to make sure that all the countries in Europe could be friends and work together after a lot of bad things happened in the past like wars and fights.
He said that instead of countries trying to do everything on their own, they should work together to make things better for everyone. Imagine if you and your friends wanted to build a fort, but each one of you only had a little piece of wood. If you all worked together and shared your pieces, you could build something really big and cool that you could all enjoy.
That's kind of what Schuman was suggesting, but for grown-ups and countries instead of kids and forts. He thought that if countries in Europe worked together, they would be stronger and more peaceful.
So, the Schuman Declaration was a really important first step towards what we now know as the European Union, which is like a big group of European countries that work together to create a better future for everyone.