Cholesterol is a waxy substance produced by the body and found in foods that come from animals. Cholesterol is needed by your body to make hormones, skin oils digestive juices and vitamin D. You could not live without some cholesterol in your body.
However, too much cholesterol is a major risk factor for heart disease, particularly LDL (low density lipoprotein) cholesterol. LDL causes the build-up of fatty deposits within your arteries, reducing or blocking the flow of blood and oxygen to your heart.
Resource: Keeping the Heart Healthy, In (E. Topol, ed.) Cleveland Clinic Heart Book, Hyperion: New York. pp.19-43