What is glycogen ? How is it different from starch ?

Starch is not a single compound but is a mixture of two components—a water soluble components called amylose (15–20%) and water insoluble component called amylopecting (80–85%). Amylose is a linear polymer of – D–Glucose. But both glycogen and amylopectin. Whereas amylopecting chain consist of 20–25 glucose units, glycogen chains consist of 10–14 glucose units.