HDL and LDL - cholesterol.
HDL stands for high-density lipoprotein.
LDL stands for low-density lipoprotein.
The two lipoproteins carry the cholesterol to and from cells because cholesterol can't be dissolved in the blood.
HDL cholesterol is considered the "good" cholesterol because it helps remove LDL cholesterol from the arteries and takes it to the liver to be broken down and passed from the body.
LDL cholesterol is considered the "bad" cholesterol because the low-density of the lipoprotein, it contributes to plaque - a thick, hard deposit that can clog arteries and make them less flexible
High level of HDL cholesterol may protect against heart attack and stroke, while a high level of LDL cholesterol will contribute to in increase of heart disease like heart attack or stroke.