A major difference between starch and glycogen is that starch is the form plants primarily use to store excess glucose, while glycogen is the form in which excess glucose in animals is stored.
Starch is a carbohydrate produced by all green plants and has a large number of glucose units used to store energy. Plants such as wheat, rice and potatoes are all rich with carbohydrates.
Glycogen is made by the liver and muscle cells and plays an important role in the glucose cycle. It helps cells store glucose energy and thus ensures a steady supply of energy to cells when needed.