Xbox achievements, friends, activity and the Xbox Store are all included in the app.
One of their discoveries was the inclusion of an Xbox app for PC which they say acts as a 'gateway to the entire Xbox ecosystem'. It includes Xbox achievements, friends lists, activity feeds, and the Xbox Store.
The Verge also discovered Cortana (from Halo) support, the program that acts like Apple's Siri, and is already available for Windows Phone.
Last week Xbox boss Phil Spencer tweeted that "it's time for us to talk about gaming on Windows," referring to the Windows 10 event taking place in January. So the Xbox PC app could be part of what he was hinting at.
@RpLayy I'll be focusing more on what we are doing on Win10 in January, it's time for us to talk about gaming on Windows.— Phil Spencer (@XboxP3) December 12, 2014