The Liver is most known for its ability to detoxify your blood cells (clearing your blood of harmful substances). Most people associate the Liver when mentioning alcohol. Other functions include the ability to produce proteins and bile. The proteins it produces aids in carrying fats through out the body and providing a healthy blood plasma. The production of bile helps carrying wastes, while breaking down fats in the small intestines.

For a quick synoposis, refer to this wikipedia passage:

---Quote---
This organ plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification.
----End Quote---

The liver is the largest glandular organ of the body. It weighs about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of the abdominal cavity beneath the diaphragm. Blood is carried to the liver via two large vessels called the hepatic artery and the portal vein. The heptic artery carries oxygen-rich blood from the aorta (a major vessel in the heart). The portal vein carries blood containing digested food from the small intestine. These blood vessels subdivide in the liver repeatedly, terminating in very small capillaries. Each capillary leads to a lobule. Liver tissue is composed of thousands of lobules, and each lobule is made up of hepatic cells, the basic metabolic cells of the liver.

The liver has many functions. Some of the functions are: to produce substances that break down fats, convert glucose to glycogen, produce urea (the main substance of urine), make certain amino acids (the building blocks of proteins), filter harmful substances from the blood (such as alcohol), storage of vitamins and minerals (vitamins A, D, K and B12) and maintain a proper level or glucose in the blood. The liver is also responsible for producing cholesterol. It produces about 80% of the cholesterol in your body.

Several diseases states can affect the liver. Some of the diseases are Wilson's Disease, hepatitis (an inflammation of the liver), liver cancer, and cirrhosis (a chronic inflammation that progresses ultimately to organ failure). Alcohol alters the metabolism of the liver, which can have overall detrimental effects if alcohol is taken over long periods of time.
Hemochromatosis can cause liver problems.

I hope this helps :)

Liver performs variety of functions like synthesis, interconversions storage, secretion of various
substances as follows:
Glycogenesis : Extra glucose is converted to glycogen with the help of insulin and stored either in liver
or in muscles.
Glycogenolysis : Glycogen is converted into glucose when its level falls (below 80 mg/100 ml) in the
blood. This is influenced by glucagon hormone.
Glucogenesis : Synthesis of glucose form other carbohydrates.
Gluconeogenesis : Synthesis of glucose/carbohydrates from protein and lipids (non carbohydrate
sources)
Lipogenesis : Extra protein and carbohydrates are converted into lipid for storage in adipose
connective tissue.
Deamination of protein : If protein is used for energy production, the NH2 group is removed from
amino acid as NH3, the end product keto acid, enters Kreb’s cycle.
Ornithine Cycle : Chemical part of excretion, NH3 is converted into urea in a cyclic chain of reactions
in which ornithine plays pivotal role.
Cori Cycle: Lactic acid formed in muscle is converted back to glycogen.

The liver has many functions. It is second largest organ in the body second to the skin. One function of liver storage of glycogen. This is a simplified fat that are stored in the liver and if the blood glucose level is low the liver will synthesize it to become glucose and release into the blood stream to prevent hypoglycemia. In this aspect, the liver plays a big role in controlling the glucose in the blood stream.

Another very important function of the liver is it filters all the absorbed materials in the intestine via the hepatic portal vein. After digestion when the food is simplified the microvilli found in the small intestine will absorb this simplified products and carry it towards the liver to be filtered. The liver is going to segregate the toxic and dispose it while those that are needed by the body will then be released into the blood stream to be transported to the different cells in the body that needs it.