Sett is like a soft furry blanket that is made by tiny animals called beavers. Beavers are very clever and use their strong teeth and paws to cut down trees and build dams in rivers. They use these dams to make little ponds where they can swim and play.
But the beavers also use these ponds to make their homes. They build little houses with piles of sticks and mud. These houses are called "dens".
To make their dens super cozy and warm, the beavers collect lots of grass, leaves, and bark. They stuff all these soft materials into their dens until they are really snug and comfortable.
This soft material that beavers use to make their dens is called sett. It's very comfortable and furry, just like a teddy bear. And it's also very important to other animals, like otters and muskrats, who use it to make their own homes cozy too.