Here's a breakdown:
* Baleen whales are a group of whales that use baleen plates instead of teeth to filter food from the water.
* Baleen plates are made of keratin (the same material as our fingernails), and hang down from the whale's upper jaw like a curtain.
* These plates have fringe-like edges that trap small organisms like krill and plankton as the whale swims through the water with its mouth open.
So, to answer your question more directly: Baleen is found in the mouth of baleen whales, and is used for feeding.
