On Monday, Microsoft began shipping the Cortana beta to those in the program via Apple's TestFlight service. Cortana on iOS is very similar to its Android and Windows 10 counterpart. The service will help folks do things like manage calendars, appointments, track flights, set alarms and more.
However due to Apple's restrictions, the Cortana beta doesn't include all of the features found on other operating systems. For example, opening apps or toggling settings, which Siri can do, are unavailable on iOS.
No word on when a public build of Cortana will be available, but we assume sometime early next year.
Source: TechCrunch