LDL (low-density lipoprotein) and HDL (high-density lipoprotein) are two different types of lipoproteins that carry cholesterol through the bloodstream. They play distinct roles in the body and have different effects on cardiovascular health. LDL cholesterol is often referred to as "bad" cholesterol because high levels of LDL can contribute to the buildup of plaque in the arteries, leading to atherosclerosis and an increased risk of heart disease. LDL transports cholesterol from the liver to the cells and tissues throughout the body, including the arteries. When there is an excess of LDL or the LDL particles are small and dense, they can easily penetrate the arterial walls and contribute to the formation of plaque. On the other hand, HDL cholesterol is often called "good" cholesterol because it helps remove excess cholesterol from the bloodstream and transports it back to the liver for processing and elimination. HDL acts as a scavenger, picking up cholesterol from the arteries and other tissues and returning it to the liver in a process called reverse cholesterol transport. High levels of HDL are associated with a lower risk of heart disease because it helps prevent the buildup of plaque in the arteries.