Whales are large marine mammals belonging to the order Cetacea. Their bodies are streamlined for efficient swimming, featuring a thick layer of blubber for insulation. Whales have a dorsal fin on their backs, flippers for steering, and a powerful tail called a fluke that propels them through the water. Whales possess a unique respiratory system, with blowholes located on top of their heads for breathing. They have a complex ear structure adapted for underwater hearing, and their large brains are associated with advanced social behaviors. Additionally, many species have baleen plates or teeth, depending on whether they are baleen whales or toothed whales.