Angina refers to the chest pain which occurs in the area of your heart muscle due to the shortage of oxygen. Angina has two forms: Stable Angina and Unstable Angina. While Stable angina takes place in the case of bodily exertion and decreased flow of oxygen in the heart, unstable angina is the same case but is not relieved by rest. A heart attack, also known as a myocardial infarction, occurs due to the blockage in the heart muscle, preventing it from oxygen and blood inflow.