Microsoft kicked off its BUILD 2014 conference with great announcements, including the official unveiling of its much-rumored Cortana digital assistant.

Based on a character from Microsoft's popular "Halo" series, Cortana has now become more real, launching as Windows Phone's answer to Siri and Google Now, the digital assistants for iOS and Android, respectively.

Microsoft's head of Windows Phone product and design, Joe Belfiore, took the stage at BUILD to demonstrate Cortana's features and functionality. Some rumors indicate that Jen Taylor, who voices Cortana in the Halo series, is also giving life to the new digital assistant, but Microsoft has yet to confirm this. Belfiore has described Cortana as "the world's first truly personal digital assistant," and it looks quite promising.

"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," explains Belfiore. "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."

Belfiore showed off Cortana onstage at BUILD, demonstrating that she can easily answer even dynamic questions, not just simple inquiries about the weather or sports. When asked about the story of the next Halo game, for instance, Cortana replied: "I'm quite certain you don't have proper security clearance for that information."

In addition to giving factual answers based on Bing searches, Cortana also sets reminders and goes into apps as well, whether they're Windows Phone native or third-party apps. During the demonstration, Cortana added a video to Hulu Plus queue, started a Skype call, and launched a specific person's Facebook page, after being given these tasks through voice commands.

The latest Windows Phone 8.1 software update will start rolling out to existing Windows Phone users in the next few months, while brand new phones will come rocking Windows Phone 8.1 out of the box starting in late April or early May.

For more information about Cortana, as well as many other neat features that are set to arrive with Windows Phone 8.1, check out Microsoft's blog post at this link.