The following pictures show the skull of a carnivore and the skull of a herbivore. They have different structures to assist with the digestion of the different types of foods eaten.
The carnivore's skull has incisor teeth at the front and premolars and molars along the side of the jaw. In addition, the skull has large pointed canine teeth between the incisors and premolars and a carnassial tooth near the back of the jaw. The canine tooth are important for holding prey and tearing chunks of flesh from the body. The large chunks are sliced into smaller pieces by the thin, blade like molar teeth. The jaw is used in and up and down chopping motion. The small incisor teeth pull small pieces of flesh from the bones. In dogs, the carnassial molars break bones to release marrow. The carnassial teeth can shear flesh and bone.
In the herbivore's skull, the incisor teeth cut plant material from plants for ingestion. The material, like grass, is ground between strong molar teeth, which are wide and may be flat or ridged. The jaw is moved in a circular motion crushing the plant material as the top and bottom molars slide across each other. Herbivore's skull does not have canines as they are not needed to hold food and would make circular chewing difficult.
A similarity between the skulls is that herbivores and carnivores have more than one type of tooth and the teeth have specialised functions.
The differences relate to the food they eat. The cells in plants are tough so physical digestion is important for herbivores. Firstly sharp wide incisors cut plant material. The food must be crushed and ground so the molar teeth are large. There is a large diastema so food can be moved and mixed with saliva. Chewing is a side to side movement to crush plants which increases surface area for enzymes.
Because animal protein is easily digested, physical digestion is less important in carnivores. The teeth and jaws cut lumps of meat to smaller pieces. Long pointed canines hold prey and rip meat from bones, sharp incisors cut them into smaller pieces and thin blade like molars cut meat into small lumps. They have no diastema as the jaw moves up and down to slice meat.