Sharks are fish. They are vertebrates, meaning they have a rigid backbone. They are also very ancient beasts – this Class of aquatic animals has existed on the earth for more than 400 million years. They live in water and their bodies are covered in scales. To swim, they move their tails from side-to-side.
Whales on the other hand are mammals, a wholly different class of vertebrates. The history of these hairy creatures goes back about half as long as fish: they appeared on the earth about 180 to 200 million years ago. On an evolutionary time scale, whales are just babies, having appeared only about 50 to 60 million years ago! Compared to sharks, whales have smooth skin (no scales), and their tails move up-and-down for swimming.