Since iOS 4.2, the iPhone and iPad offer the AirPrint function. AirPrint is compatible only with newer printers models, but still you can retrofit conventional printers with AirPrint using the AirPrint Activator.
What is AirPrint?
AirPrint is a technology developed by Apple. It provide an interface that enables communication between Apple devices and printers. Print jobs can be sent quickly and easily over Wi-Fi to compatible printers.