Final answer:
Prinzmetal's angina, also known as variant angina, occurs at rest, often during sleep, while angina pectoris, also known as stable angina, is precipitated by exertion and is relieved by rest or nitroglycerin.
Step-by-step explanation:
Prinzmetal's angina, also known as variant angina, is a type of angina pectoris that occurs at rest, often during sleep. It is caused by coronary artery spasms which can lead to temporary narrowing of the arteries and reduced blood flow to the heart muscle. On the other hand, angina pectoris, also known as stable angina, is typically precipitated by exertion and is relieved by rest or the administration of nitroglycerin.