Subtracting numbers means finding out how much less one number is than another number.
For example, if you have 5 pieces of candy and then you eat 2 pieces, how many pieces do you have left?
To find out, you would start with 5 and then take away 2, which means you have 5 - 2 = 3 pieces of candy left.
So, subtraction helps you find out the difference between two numbers, just like finding out how many pieces of candy you have left after eating some.