High-density lipoproteins (HDL) are a type of cholesterol found in the bloodstream. They are often referred to as "good" cholesterol because they help transport excess cholesterol away from the arteries and back to the liver, where it can be processed and removed from the body. Higher levels of HDL are associated with a lower risk of heart disease. HDL is composed of proteins and lipids, making it denser than other types of lipoproteins, such as low-density lipoproteins (LDL). Regular physical activity, a healthy diet, and maintaining a healthy weight can help increase HDL levels, contributing to overall cardiovascular health.