Angina pectoris is a clinical syndrome characterized by recurrent pain in the chest, shoulder, jaw, back, or arm. This condition is caused by a decrease in blood flow to the heart, and pain results when the oxygen demands of the heart cannot be met by the available oxygen in the blood vessels supplying the heart. If you have a history of high blood pressure and high cholesterol, you are at a higher risk of experiencing this type of chest pain. The pain can be mild or severe, and is described as a "crushing" or "squeezing" sensation.

There are two major types of angina:

Stable angina is defined as chest pain that occurs with exertion, and has not changed in frequency or severity over time.

Unstable angina, on the other hand, has variable chest pain that occurs in episodes and can often occur at rest. If there is any change in the amount of exertion needed for chest pain to occur, this too can be defined as unstable angina.

Reference

Gibbons RJ, Abrams J, Chatterjee K, et al. ACC/AHA 2002 guideline update for the management of patients with chronic stable angina: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for the management of Patients with Chronic Stable Angina). 2002.