It's a PVC film coated with self-adhesive on the back. It comes with a variety of colors, is waterproof and has no adhesive residue. 

Instructions:
1.  DesignDraw or trace the design.
2. CutPlace the shiny plastic side up on the cutting mat.Load the cutting mat into the machine and cut your design with a pointed blade.3. WeedRemove the workpiece from the cutting mat and remove the excess lettering film with a weeding tool.4. PastePeel off the pattern from the release paper, paste it to the desired position, smooth it evenly, and eliminate the bubbles to finish pasting.