Copy-number variation is like having different numbers of toys.
Just imagine you and your friend have toy blocks. If your friend has 10 blocks and you only have 5 blocks, that's a copy-number variation.
This is the same in our bodies. We have different copies of genes that help us grow and stay healthy. Some people might have more copies of a certain gene than others, and some people might have fewer copies.
These copy-number variations can affect our health in different ways, just like having more or fewer toys can affect the games you play. Understanding these variations can help us learn more about genetic diseases and how to treat them.