As reported by engadget,
While Microsoft undoes Cortana’s expansion to other platforms like Android or iOS, it’s making the voice assistant more powerful within Windows 10. A version of the OS currently available to Insider program beta testers includes the ability to find files on your PC simply by asking for them. Enterprise users with OneDrive or SharePoint can also locate files in network drives that they have access to, but the key here is that it can find information without needing every specific detail.
According to the blog post, just the part of a file name or name of an author can be enough for the AI to figure out which document you need. “Hey Cortana, opening marketing deck,” and “Hey Cortana, open budget Excel from Anthony” are two examples, along with ‘find recent files” to pop up the last few items you’ve accessed.