HDL is an acronym for High-Denisty Lipoprotein. HDL's main function is to carry cholesterol from other parts of the body back to the liver where it is eliminated from the body. HDL is considered the "good" cholesterol because higher levels are associated with decreased risk for heart disease.
While higher is better when it comes to your level of high-density lipoprotein, or HDL, the opposite is also true---low HDL is a risk factor for heart disease, according to the American Heart Association (AHA).