Cardiology is the branch of internal medicine dealing with disorders of the heart and blood vessels. The field is commonly divided in the branches of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians specializing in this field of medicine are called cardiologists.
Cardiologists should not be confused with cardiac surgeons who are surgeons who perform cardiac surgery - operative procedures on the heart and great vessels.
See Wikipedia, Cardiology.