HDL is short for high-density lipoprotein. Each bit of HDL cholesterol is a microscopic blob that consists of a rim of lipoprotein surrounding a cholesterol center. The HDL cholesterol particle is dense compared to other types of cholesterol particles, so it's called high-density. Cholesterol isn't all bad. In fact, cholesterol is an essential fat. It provides stability in every cell of your body. To travel through the bloodstream; cholesterol has to be transported by helper molecules called lipoproteins. Each lipoprotein has its own preferences for cholesterol, and each acts differently with the cholesterol it carries. Experts believe HDL cholesterol may act in a variety of helpful ways that tend to reduce the risk for heart disease: