Okay, imagine you and your friends are playing a game and you all have toys that you really like. You notice that one of your friends has a really cool toy that you really want. You ask if you can borrow the toy to play with it and your friend says yes, but only if you let them borrow one of your toys in exchange. This is what is called a trade or an agreement.
Many years ago, during World War II, two countries, the United States and Great Britain, also made an agreement like this. The United States had some old Navy ships called destroyers and Great Britain really needed them to protect their country during the war. In exchange, Great Britain agreed to let the United States use some of their own military bases to help protect the United States from its enemies.
This was called the Destroyers for Bases Agreement because the United States was trading their old destroyers for new bases to protect the country. It was a way for both countries to help each other out during a difficult and dangerous time.
In the end, the agreement was a success and both countries benefited from it. The United States was able to protect its people better with the new military bases and Great Britain was able to protect its own country and people better with the old destroyers. This is what an agreement or trade can do - it can help both sides and make things better for everyone involved.