Windows Phone’s intelligent (and voice-controlled, if you like) assistant is called Cortana, after the AI character from the Halo videogames series. Cortana is analogous to Siri on an iPhone.
When you invoke Cortana from a Live Tile, you’ll see some information that’s relevant to your interests (Cortana will ask about those interests after you set up your device, and then periodically when you’re interacting with her).
As with Siri, Cortana can find nearby locations, restaurants, facilities and so on. Suggestions are displayed for further interactions. The voice recognition accuracy is excellent, in my experience.
The assistant will also tell jokes, and respond to references to the Halo franchise, much as Siri knows about Apple products and personnel.
Cortana has a notebook of knowledge about the device’s user, which you can inspect and configure at any time. There’s an explicit interface for what the device knows about you, which is a pleasant change from Siri’s mostly opaque sense of context.
The assistant will recognise your home address based on your usual location during evening hours, and will confirm this assumption with you. You can also add more locations yourself.
Cortana will also learn about your most frequently-contacted acquaintances, and will make assumptions about family members based on shared surnames, and other cues. Close contacts are added to your inner circle, and can be allowed to break through even if you’ve set your phone to not disturb you during certain hours.
Windows Phone’s equivalent of an iPhone’s Do Not Disturb feature is called Quiet Hours, and Cortana uses your inner circle list when screening calls, texts, and related notifications.
You can tell Cortana to automatically respond to screened contacts, telling them that you’re busy at the moment. She can also ask inner circle members if they’d like their text message to break through to you, on a case-by-case basis.