Burls are irregular growths in trees. When they occur, they're usually on trunks, or within roots. They yield beautiful figured woods that make stunning furniture. This page shows a few examples of burls, and how they look in a piece of furniture.
Burl Growths on a Tree Trunk
Walnut Burl
Laurel Burl
Amboyna Burl
Mappa Burl
Giovaniello Desk Detail
This standing desk uses Laurel Burl. Here, Laurel Burl is paired with straight grain walnut and ebony inlay lines.