A beaver is a water- and land-dwelling animal with a very broad tail, short fur, and prominent front teeth. Beavers are famous for their ability to build dams across rivers and streams.
Beavers are actually rodents, so they are related to mice and rats, though they're much larger. Their long teeth make it possible for them to chew through even broad tree trunks, felling them across bodies of water to create dams. This provides the beavers with a safe home or lodge, protected by the ponds they've created and usually accessible only underwater. The word beaver has a Proto-Indo-European root that means "brown" or "bright."