NFC technology is regulated by Near Field Communication Forum which standardizes NFC communication between devices -- how they pair, share data and allow a secure transaction to happen.NFC Forum develops and certifies device compliance with NFC standards . NFC operate on ISM band of 13.56 MHz Frequency. NFC communication range is up to 10 cm. But, this is limited by the antenna and power radiation design. Most devices work within a range of 10mm. NFC Shield antenna is designed to work within a range of 1cm. NFC Shield provides all necessary circuitry for PN532 like 27.12Mhz crystal, power supply. It also beaks-out the I/O pins of PN532 for easy access. The communication between Arduino and NFC Shield is via SPI.