There are four main types of teeth - incisors, canines, premolars, and molars - each with a different function. Incisors cut and bite food, canines hold and tear food, premolars crush and grind soft food, and molars chew and grind hard food. Different animals have different teeth depending on whether they are herbivores, carnivores, or omnivores, with herbivores having teeth adapted for grinding plants and carnivores having teeth for tearing meat.