Thneeds are fictional products from Dr. Seuss's book, "The Lorax." They are versatile items made from the fibers of the Truffula tree, which can be used for various purposes, such as clothing, rugs, and even toys. In the story, the demand for Thneeds leads to the overharvesting of Truffula trees, resulting in environmental degradation. The character The Lorax speaks for the trees and warns about the consequences of exploiting natural resources, highlighting the importance of sustainability and conservation.