Cholesterol is a waxy fat that is always present in our bodies.

Some of our cholesterol comes from the food we eat, but the liver makes most of it (about 80 percent).

A certain amount of cholesterol is vital for good health.

Low cholesterol levels can indicate problems such as malnutrition or a thyroid disorder.

The medical term for an excessive amount of cholesterol in the blood (over 240 milligrams per deciliter [mg/dL]) is hypercholesterolemia.

"Good" cholesterol is HDL (high-density lipoprotein). "Bad" cholesterol is LDL (low-density lipoprotein).

HDL is good because it reduces LDL.

LDL is bad because it hardens and clogs the arteries. That can lead to heart disease, heart attack or stroke.

Triglycerides are another type of blood fat that is needed by the body but can contribute to heart disease when present in large amounts.

Some experts say women need more HDL cholesterol than men because women have increased risk of heart attack after menopause.

Your cholesterol levels are revealed by a blood test, which may be called a blood fat profile, a lipid profile or a cholesterol test.