Powered by Bing, Cortana is the only digital assistant that gets to know you, builds a relationship that you can trust, and gets better over time by asking questions based on your behavior and checking in with you before she assumes you’re interested in something. She detects and monitors the stuff you care about, looks out for you throughout the day, and helps filter out the noise so you can focus on what matters to you. Cortana will launch shortly here in the U.S. first as a “beta,” and then will launch in the US, the U.K. and China in the second half of 2014 with other countries to follow afterwards into 2015.Microsoft Launches "Cortana" Personal Digital Assistant On Windows Phone
In Windows Phone 8.1, you get to Cortana by either a Live Tile on your Start screen or by pressing the search button on your device. This will take you to Cortana Home. To interact with Cortana, you can either speak or type—if you’re in a meeting, just type and Cortana won’t talk out loud. But if you ask her a spoken question, she’ll answer verbally and even carry on a natural conversation.