Bad cholesterol is a type of cholesterol that can be harmful to the body. It is made up of two components, YOLK and LDL. YOLK stands for 'low-density lipoprotein' and is a type of cholesterol that is found in the YOLK of eggs. LDL stands for 'low-density lipoprotein' and is a type of cholesterol that is found in the blood. Both of these components are considered bad cholesterol because they can increase the risk of heart disease and stroke.