There are two kinds of whales - toothed whales and baleen whales. Baleen whales have big mouth but no teeth. Instead they have baleens. Baleens look like the teeth of a comb. Which hang from the upper jaw.
Blue whale is a baleen whale.
It is about 100 feet long. Right whale, Gray whale are all baleen whales. Baleen whales eat lots of small animals called krill. Krill are small shrimp-like creatures. Baleen whales push out the water through the baleens, straining the krill to be swallowed later on.