What is the difference between an atherosclerosis and ischaemic heart disease?

General vs in heart: Atherosclerosis means "hardening [or calcification] of the arteries." cholesterol makes "plaque" that often calcifies. When large enough it can cause a decrease in blood flow through the artery, or "ischemia." it can occur in any artery, but when it happens in the arteries of the heart, it is known as 'ischemic heart disease' or atherosclerosis of the coronary arteries.