In math, representation means showing something in a specific way so that we can understand it better.
Let's say you have 10 apples and your friend has 5 apples. We can represent this using numbers. We write down that you have 10 apples and your friend has 5 apples. This is a way of representing the number of apples you both have.
But we can also represent this information using pictures. We can draw 10 apples next to your name and 5 apples next to your friend's name. This is another way of representing the same information.
In math, we use different types of representations depending on what we're trying to understand or communicate. Sometimes we use numbers, sometimes we use pictures, sometimes we use symbols, and sometimes we use graphs or charts.
Overall, representation is all about finding the best way to show something so that we can understand it better.