Cortana has been designed to find the right information at the right time and to make recommendations based on the user's preferences. Over time, Cortana gets to know the user better and its answers become more user-specific. Already available in Windows phones, it allows users to interact at any time with Cortana using the spoken word or by typing a message.
Cortana for iOS is not likely to be available to the general public for several months. It will then be competing with other virtual personal assistants, including Siri.
Apple's Siri also responds to the spoken word. It can respond to any verbal request, such as operating the device in which it is installed, answering questions about the weather, etc.
Google Now is also available in iOS devices. The app is linked to search history, calendar, e-mails and location so it can offer more precise answers to queries.
Meanwhile, a report fom Wareable also surfaced this week suggesting that Microsoft could have a Cortana-based wearable in the works. The report names a device known 'Clip' could be a 'hearable' for consumers, essentially putting Microsoft's personal assistant in the wearer's ear.