It's called the Cortana voice assistant for Microsoft's smartphone - Reuters

A little ‘Siri, a little’ Google Now: could come as early at the next update of Windows Phone

users of smartphones with Microsoft’s Windows Phone will have their ‘virtual assistant’. For now, its code name is ‘Cortana’, borrowed from your Avatar female video game Halo, and will be a mix of Siri – Apple’s assistant – and Google Now Big G. It writes the blog The Verge, according to the which the news will be included in the new features that come with the Windows Phone 8.1 update expected in the coming months.

Cortana, writes the blog, is actually `popped ‘last year when a Microsoft employee lost a phone that was testing on Windows Phone 8.1. Now other rumors indicate that Cortana should replace the built-in search in Bing and will be the `virtual assistant ‘, combining the elements of Siri voice and those` contextual’ Google Now. It will be a circular icon that comes alive when speaking or `thinking ‘and respond to the questions posed by users based on the data coming from Bing search engine, but not only, also from Foursquare and other applications. The goal is to provide users with information in context `’a little’ how does Google Now, based on such commitments you have on the agenda, at your location or travel plans. Using the function “Notebook” you can decide how many and which collected data from their smartphone can be used by Cortana. (ANSA).