Devore is a process of using chemicals to dissolve natural plant fibers (like rayon, acetate or cotton) but leaving synthetic or silk fibers behind.
The plant fibers dissolve, leaving a sheer mesh of the synthetic – creating a lacey, elegant fabric.
Here are two different videos explaining some basic devore techniques.  In the first one, fiber artist Dionne Swift explains the basic process, and the fabrics used:
The second video shows how to use devore to create a cutwork piece.
Just remember, any time you’re using chemicals in your studio – take the appropriate precautions!