Cholesterol is a lipoprotein—a waxy substance produced by your liver and carried in your bloodstream. It's also found in foods from animals (meat, dairy, etc.). Cholesterol is a necessary nutrient: Your body can't function well without it. But too much can lead to blocked heart arteries. There are different kinds of cholesterol:
High-density lipoprotein (HDL) protects against heart disease. Your level should be at least 40. The higher, the better.
Low-density lipoprotein (LDL) is a risk factor for heart disease. Your level should be less than 100.
Triglycerides, also bad, are fat molecules that accompany cholesterol. High triglyceride levels are bad for the heart, because they can crowd out the good cholesterol.