High density lipoproteins (HDL): the "good" cholesterol. HDL carry cholesterol in the blood from other parts of the body back to the liver, which leads to its removal from the body. So HDL help keep cholesterol from building up in the walls of the arteries.
For adults, the HDL-Cholesterol Levels are measured to determine possible health risks. Less than 40 mg/dL indicates a major risk factor for heart disease; where an HDL of 60 mg/dL and above is considered protective against heart disease.