Cardiology is a branch of internal medicine. A cardiologist is not the same as a cardiac surgeon. A cardiac surgeon opens the chest and performs heart surgery.
A cardiologist specializes in diagnosing and treating diseases of the cardiovascular system. The cardiologist will carry out tests, and they may perform some procedures, such as heart catheterizations, angioplasty, or inserting a pacemaker.
Heart disease relates specifically to the heart, while cardiovascular disease affects the heart, the blood vessels, or both.