The difference between HDL and LDL cholesterol lies in their functions and health implications. HDL (high-density lipoprotein) is known as "good" cholesterol because it helps transport cholesterol from the arteries to the liver for excretion, reducing cardiovascular risk. LDL (low-density lipoprotein), often referred to as "bad" cholesterol, carries cholesterol to cells but can lead to plaque buildup in arteries when levels are too high. Maintaining a healthy balance between HDL and LDL is crucial for cardiovascular health, often influenced by diet, exercise, and lifestyle choices.