How Do The Arteries Carry Blood Away From The Heart And Veins Carry It Back To The Heart?

The heart actually consists of two pumps and pumps blood in two circles, firstly around the lungs to collect oxygen, pulmonary circulation, and then around the rest of the body, systemic circulation. Blood circulates because of the pressure caused by the heart's pumping action, high pressure when exiting the heart into the arteries, much reduced pressure when returning to the heart in the veins. As well as residual pressure blood flow in the veins is assisted when we move our bodies and constrained when we don't move our bodies, that's why when we sit still for a long while on an aircraft there is a risk of blood clotting in our leg veins, deep vein thrombosis DVT.
an adult heart pumps in the region of 5 litres of blood every minute, and that's only when we are resting!

It all goes in one big circle and after blood is taken from the heart it gets oxygenated to let muscles work then when it has been used it goes back round the circle to do it again.