Office 365 through the Store is Microsoft's port of Office via the "Centennial" desktop bridge. Those using this version will get almost all features of the traditional Win32 version of Office, plus regular updates to Office.
Testers Anthony Ruiz (@tonytech) and Keinan Thompson (@keinanthompson) posted to Twitter on the evening of August 31 the invitations they received for the new version of Office. That invitation claims this is a "small invite-only preview program to test a new way to get Office 365 -- through the Windows Store."
Microsoft is making this limited preview available on any Windows PC running Windows 10 Creators Update or later, according to the invitation.
In spite of the wording of the limited preview invitation, Office in the Windows Store suite is not identical to the full desktop Office suite. Those using Office in the Windows Store can install the 32-bit version only, not the 64-bit version. Users of the Office in the Windows Store release cannot use COM add-ins on Windows 10 S, but can on other Windows 10 versions. And the OneNote app that is installed will not be the OneNote 2016 version; it will be the Universal Windows Platform version.
Office 365 Personal, Office 365 Home, Office 365 for Education Plus, and Office 365 Education E5 users will all have access to the Office in the Windows Store apps during the preview period, Microsoft officials said previously.