Microsoft has published several of their free desktop Windows apps in the Windows Store. The free apps are available for Windows 10 PC owners with the latest Insider preview builds.
The Windows Store links (via MSPU) include the classic bare-bones word processing app WordPad, along with the Microsoft Character Map app for viewing all of a font's letter, numbers and symbols. There's also the Windows Fax and Scan app for basic scanning and faxing features. Finally, there's the XPS Viewer app for checking out XPS documents.
All of these apps are just for PC owners; Microsoft did not make them compatible with Windows 10 Mobile. They also don't have any special features; aside from the fact they come from the Windows Store, they will work just like their regular desktop counterparts.