Imagine you have two groups of squares. One group has blue squares and the other group has red squares. Each blue square has a matching red square. This means that every blue square has a partner red square that looks exactly the same size and shape.
When you line up the blue squares and the red squares next to each other, you will see that they match up perfectly. This is what we call "corresponding squares". It's like having a pen pal who lives in a different country but you both have the same things like toys, pets, and clothes.
So, in summary, corresponding squares are two groups of squares that match up perfectly with each other, just like two pen pals that have the same things.