The liver does quite a lot of "housekeeping". It is responsible for a lot of energy metabolism: Gluconeogenesis (the synthesis of glucose), Glycogenolysis (the breakdown of glycogen into glucose), Glycogenesis (the synthesis of glycogen from glucose).
It is important for protein degradation as well as for amino acid synthesis, as well as in the lipid metabolism. This includes synthesis of cholesterols, lipoproteins and fatty acids. The liver produces a number of factors important for coagulation including prothrombin and a number of hormones.
It is very important for the breakdown of Bilirubin and insulin, and it detoxifies the body via the cytochrome P450 system. It is storing some substances as vitamin A, B12, D and K as well as iron and important for their regulation. For more details read the corresponding Wikipedia article on the liver.
So easy speaking does the liver a lot of maintenance in the human body which is important for a lot of different processes.