What are polysaccharides and what are the most abundant ones?

Polysaccharides are formed by hundreds of monosaccharides linked by glucosidic bonds.
The most abundant polysaccharides are starch, glycogen, and cellulose.
Starch is the energy reserve polysaccharide of plants, while glycogen is the energy reserve polysaccharide of animals.
Cellulose is composed of glucose units linked by a slightly different type of glucosidic bond and is not soluble in water.