It is named after Cortana, an artificial intelligence character in Microsoft's Halo video game series, with Jen Taylor, the character's voice actress, returning to voice the personal assistant's US-specific version.
Microsoft isn't creating a separate app for Cortana on the desktop, it will essentially replace and complement the existing search experience that's available in Windows 8.
Cortana's features include being able to set reminders, recognize natural voice without the user having to input a predefined series of commands, and answer questions using information from Bing (like current weather and traffic conditions, sports scores, and biographies).
Cortana also includes a music recognition service. Cortana can also roll dice and flip a coin by asking the commands "roll a dice" (one die), "roll the dice" (two dice), and "flip a coin", Concert Watch is a feature that helps Cortana determine which bands or musicians you are interested in by monitoring your Bing searches. Cortana also integrates with the Microsoft Band for Windows Phone devices if connected via Bluetooth.
On the Microsoft Band Cortana can make reminders and bring phone notifications
Cortana features a "do-not-disturb" mode in which users can specify "quiet hours", something that is already available for Windows Phone 8.1 users.
Users can change the settings so that Cortana calls users by their names (or nicknames).It also has an extensive library of Easter Eggs, consisting of witty and pre-determined remarks