In Short

Cortana is the name for the intelligent personal assistant and knowledge navigator for Windows Phone 8.1 and Windows 10. Cortana builds off Microsoft's previous voice technology called TellMe, purchased by Microsoft in 2009.

Cortana competes against Apple's Siri and Android's Google Now voice assistants.

The name 'Cortana' comes from the fictional, artificially intelligent (AI) character in the Halo video game series. The first evidence of Cortana's existence was found in June 2013 in the Windows Phone Central forums, appearing as 'zCortana' from a developer device that was accidentally sold to a non-Microsoft employee.

Naming and Voicing

The name Cortana was reserved for the AI in Microsoft's Halo gaming series. While there was a desire to call Microsoft's next-gen personal assistant Cortana as an official name, it was not clear that the company could do so, due to numerous marketing and trademark concerns.

However, on April 4 2014, Microsoft finally unveiled Cortana to the public during Build 2014. Microsoft chose the name Cortana due to a popular groundswell of fans who requested the name.

Jen Taylor, who currently voices Cortana in the Halo games, also voices the knowledge navigator for Windows Phone 8.1.

Look and Features

The current look of Cortana is both futuristic and minimalist, being represented as an orb with animation. From a pre-release description of Cortana by an inside source:

"The personality of Cortana is currently represented by a circle graphic that expresses what it's doing (searching, identifying music Cortana is currently represented by a circle graphic that expresses what it's doing (searching, identifying music à la the current Bing music listener built into Windows Phone, etc.) by various animations like spinning, flipping, etc. …more animations [have] come in over time, and the color is based on your theme color."

Cortana can integrate with third-party apps via a new API introduced by Microsoft at their 2014 Build conference. For instance, users can say "Foursquare...checkin" and the personal assistant launches the Foursquare app and brings up locations around you to choose for checking in.

Cortana can set reminders, track your flights, tell you the weather, send messages, and answer questions. All searching on Windows Phone 8.1, including Internet Explorer, is handled through Cortana, which itself is powered by Bing.

Various sections of Cortana can also be pinned to a user's Start screen, including Weather, Reminders, and News for quick access. The app, upon launching, can optionally deliver a 'Daily Glance', which includes your weather, traffic, and headlines.

Cortana can also make NFL and other predictions and speak Klingon.

Finally, another change is how users start Cortana as the app is now initiated via the Search key. Users will no longer have to hold down the Start key to launch the voice assistant.

Forthcoming features

The Cortana team, led by Marcus Ash, is adding new features to Cortana roughly every two weeks. Those new features are added to the Cortana 'What's New' page hosted by Microsoft.

Evidence for package tracking by Cortana was found in the Windows 10 registry, suggesting that this is a forthcoming feature.

Starting with the Lumia Denim update later in 2014 for the Lumia 930 and Lumia 1520, users will be able to activate Cortana via passive voice, meaning they do not physically have to launch the voice assistant. Instead, users can simply say 'Hey, Cortana' and the phone, through passive-voice technology, will wake to take the request. This feature is dependent upon the Qualcomm Snapdragon 80x chipset series and SensorCore.