Cortana will likely prove most useful for users of Windows on desktop and mobile, where Microsoft has incentive to differentiate its own products and can easily integrate Cortana at the system-level, but here’s the company’s description of what Android users can do with it:
The Cortana app can do most of the things Cortana does on your PC or on a Windows phone. With the app, you can manage your hectic lifestyle by setting and getting reminders, searching the web on-the-go, tracking important information such as flight details as well as starting and completing tasks across all of your devices.
We’ve already dived in to Cortana extensively through hands-on videos and a comparison with competing assistants including the aforementioned Google Now and Hound, so check those out if you’re curious about how it stacks up. Our own Stephen Hall has concluded that the switching costs of moving to Cortana, which doesn’t have the kind of access to Google services that Google’s own Now does, are too high to justify the move, even when you can now make Cortana accessible from the Android home button. That’s how the mobile ecosystem is these days: Companies differentiate with tight top-to-bottom integration, and try everything to lock you into their own garden.
To download the official Cortana beta, hit up the Google Play beta URL for it (a new functionality of Google Play).