Glycogen is a storage polysaccharide, which means it is made up of a chain of many monosaccharides. It is a storage polysaccharide because it is stored in the liver and muscle cells to be used as a source of energy later on.
Our body uses glucose for energy, but when it is not used up, it is stored in the liver and made into glycogen. When the body needs an extra boost of energy, it will use glycogen, especially when there is no other source like glucose, around.
