Twisted Nematic (TN) This technology consists of nematic liquid crystal sandwiched between two plates of glass. When power is applied to the electrodes, the liquid crystals twist 90°.
Super Twisted Nematic (STN) This technology has rapidly become a standard for most monochrome passive-matrix LCDs. It uses the same principle as TN displays but uses less power and is typically less expensive. The liquid crystals in STN technology have a 210° - 270° twist which allows for a broader transition region for gray scaling. STN displays can also be made purely reflective for viewing under direct sunlight.
Film Compensated Super Twisted Nematic (FSTN) This technology uses a film compensating layer between the STN display and rear polarizer. This additional film increases the overall sharpness and contrast of the display.