Apple introduced AirPrint in 2011 as a standard way to enable wireless printing from iPads, iPhones, and Macs without the need to install drivers. Almost all new printers on the market today already support AirPrint. If you have an older printer, however, and it doesn't support AirPrint, Printopia will fix that.
To read more about AirPrint, see Apple's About AirPrint support article.