ITO (Indium-Tin-Oxide) is a clear, conductive liquid/film and here it is used as a coating on a flexible plastic (PET) sheet. ITO is a very interesting material, also used in scientific research and LCD/OLED manufacture. Only one side of ITO (Indium Tin Oxide) Coated PET Plastic - 100mm x 200mm is coated in ITO, so you can use the flat of a blade or similar to scrape away some of the film to create traces. It may also be possible to use a laser cutter to pattern it.
It's not possible to solder to ITO (Indium Tin Oxide) Coated PET Plastic - 100mm x 200mm, but you can use conductive inks, paints, copper tape (with conductive adhesive) and alligator clips to make contact.
Adafruit Web Site: http://www.adafruit.com/products/1309