Cholesterol like oil is insoluble in blood and therefore it needs to be carried from one part to other part of the body.  These carriers are called lipoproteins fat (lipid) +protein.  This is of two types. Low density (LDL) and High density (HDL).

LDL Bad cholesterol – It helps to form plaques in the blood vessels, that are hard and makes the vessel thicker and less flexible.

HDL Good cholesterol – This carries the bad ones to liver for breaking down and to be excreted from the body.