Whales belong to the order Cetacea.  There are two different types of whales: toothed whales and baleen whales. Baleen whales do not have teeth. Instead they have fibrous plates called baleen, which they use as a filter to trap their food. They do this by taking in a large mouthful of water and plankton, krill or fish and push the water out through the baleen plates. These animals are too big to fit through the plates and therefore become trapped in the interior of the baleen plates. The whale then uses its tongue to gather and swallow all of the trapped food inside of its mouth. Toothed whales catch and swallow their prey one by one, grasping it with their teeth. In fact, dolphins are toothed whales.