Answer:
If two functions are the inverse of each other, they reverse or undo what the other function does. To give the simplest example, addition and subtraction are inverse functions, so that if you start with 7 and add 3 you get 10, and then if you subtract 3 you are back to 7, which is what you started with, so the subtraction reverses the effect of the addtion (if you subtract the same amount, which in this example was 3).