What is the difference between hdl and ldl cholesterol levels?

Good vs Bad: Hdl is high density lipoprotein. Hdl provides a vital service in removing cholesterol from the vasculature, and accelerating its excretion in the liver. In general, an HDL >50 is recommended. Ldl is low density lipoprotein. This harmful type of cholesterol leads to atherosclerosis, which can lead to stroke, heart attack, or peripheral arterial disease. In general, an LDL <130 is recommended.

Directional: Total serum cholesterol is made up of several component lipoproteins. Amongst these are fractions: hdl-c is the "good", which you want to be as high as possible and ldl-c is the "bad" which you want to be as low as possible. Lifestyle and, if needed, drug therapy, can help towards those goals.