Siri is included for free as part of Apple's iOS, the operating system that powers the iPhone and iPad. Siri began as an app available on the iTunes App Store prior to being purchased by Apple and integrated into iOS 5 and up.
Siri is a voice recognition software that is capable of accessing various functions within iOS. Using Siri, users can search the Web, make phone calls, send texts, launch apps and take notes in addition to hundreds of other tasks. Siri's artificial intelligence is powerful enough to make adjustments to the pronunciation of names when corrected and remember relationships between the operator and the phone's contact list.