The low-density lipoproteins transport cholesterol from the liver to specific cells and the high-density lipoproteins remove excess cholesterol from the body cells and return it to the liver where it can be excreted in bile.
Density, in terms of matters indicate the mass per unit volume, for example oil will be more dense than water. For electronics high density indicates more closely packed with components. For example...
well a low density means that there is less mass compacted into a given area. high density is just the opposite, where much mass is compacted into an area. for example wood has lots of air pockets in...
this is a molecule carrier system which transports cholesterol back to the liver for recycling. It is thought having high HDL levels is protective against heart attacks and stroke.