Basically the main fuction, as others have said is to pump blood around the body... it s hard to give a short answer for this question, so let me break it down into left and right side; The right-hand side of the heart receives de-oxygenated blood from the body tissues (from the upper- and lower-body via the Superior Vena Cava and the Inferior Vena Cava, respectively) into the right atrium. This de-oxygenated blood passes through the tricuspid valve into the right ventricle. This blood is then pumped under higher pressure from the right ventricle to the lungs via the pulmonary artery The left-hand side of the heart receives oxygenated blood from the lungs (via the pulmonary veins) into the left atrium. This oxygenated blood then passes through the bicuspid valve into the left ventricle. It is then pumped to the aorta under greater pressure.This higher pressure ensures that the oxygenated blood leaving the heart via the aorta is effectively delivered to other parts of the body via the vascular system of blood vessels.