High-Density Lipoproteins (HDL) are a type of cholesterol found in the bloodstream. They are often referred to as "good" cholesterol because they help remove excess cholesterol from the body and transport it to the liver for disposal. Higher levels of HDL are associated with a lower risk of heart disease. HDL particles are smaller and denser than other types of lipoproteins, such as Low-Density Lipoproteins (LDL), which are considered "bad" cholesterol. Maintaining healthy HDL levels can be achieved through regular exercise, a balanced diet, and avoiding smoking.