There are three main classifications of rice based on grain length: long, medium, and short. Long grain rice is the skinniest, short grain is short and round, and medium grain falls in between. Each type has different textures and common uses - long grain is fluffy and absorbs sauces well, short grain is sticky and used for sushi and rice pudding, and medium grain is versatile. There are thousands of rice varieties worldwide with different flavors, aromas, and textures suited to various dishes.