It’s just a way of checking your answer, like using a calculator, if you graph something (correctly) and compare your answer (something that can be graphed) to your graphed number you can check your answer
It helps you see the visual move of what you were doing. If you weren't moving anything it would help you see if it is true or false. Say you put a dot on the origin (0,0), then you have to go (x+7,y+3) then moving it on a graph would help show you. So overall it's a visual help to people.
