1- Monosaccharides: Simple sugars, the simplest carbohydrate form. In general, the basic molecular formula is (CH2O)n. Monosaccharide' function: a source of energy for organisms. Examples: Glucose, galactose, and fructose.
2- Disaccharides: consist of two monosaccharides joined together by a covalent bond. This bond is generally between the number 1 carbon of one monosaccharide and the number 4 carbon of the other molecule. Disaccharides' function: a nutritional source of monosaccharides. Examples: sucrose or table sugar, maltose, and lactose.
3- Polysaccharides: composed of thousands of monosaccharides. The addition of new monosaccharides could continue indefinitely making a huge molecule forming a long (and branched via the 6- carbon) chain of glucose molecules. This long chain is known as a polysaccharide. Polysaccharides' function: an easily accessible storage form of glucose. Examples: starch and glycogen.