What is the difference between good cholesterol and bad cholesterol?

Cholesterol is a fatty substance present in all animal
tissues. It belongs to a class of chemicals which are a type of lipid. In humans
cholesterol makes up an important part of membrane of each cell in the body. Cholesterol
is also essential in making of bile acid produced by the liver, and in making of certain
hormones.

In addition, the liver uses cholesterol to make
bile acids, which aid digestion.  The body also uses cholesterol in the production of
certain hormones.  Hormones are chemical substances that influence many body
activities.

Cholesterol is carried in the bloodstream in
large molecules called lipoproteins. There are two such types of lipoproteins called
low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Accordingly, the
cholesterol in blood can be identifies a either LDL-cholesterol or HDL-cholesterol. High
level of LDL-cholesterol is primarily responsible for forming deposits of cholesterol in
arteries, that is a major cause of heart attacks. For this reason LDL-cholesterol is
labeled by some as bad cholesterol. In contrast, HDL cholesterol is called good
cholesterol.