There are 3 main eating habits of all animals. Animals that eat
only plants, grass, leaves etc. are called "herbivorous animals".
Examples of these would be cows, horses, goats etc in the domestic
scene and deer, zebras, girraffes etc in the wild.
Animals that eat only other animals are called "carnivorous
animals". Examples of these would be lions, tigers, snakes etc. You
won't find many tamed carnivorous animals buts cats & dogs
prefer to eat meat rather than leaves.
That leads us to the group of animals that like to eat both plants
and animals. Infact some of them like the rat, can eat almost
anything. This group of animals are called "omnivorous animals".
Most humans are omnivorous, though there are some who will eat only
plant life and avoid eating even eggs, fish and milk because of
religious or ethnic reasons. Some have made personal choices to eat
only vegetarian food because they understand that the human body is
best suited for vegetarian food and finds it comparatively
difficult to digest meat.