Project Centennial allows developers to upload classic Win32 apps to the Windows Store for use by Windows 10 users on x86 processors.
It seems Microsoft is going all in with the technology, and have uploaded numerous Windows utility apps such as Fax & Scan, Charmap, Wordpad and more to the store.
We do not know if this is merely an effort to test the technology, or of Microsoft plans in the future to let us download our Accessories from the Store (and then being asked to Rate them every time we use them).
There are rumours that Microsoft is looking to emulate x86 on ARM for use with Continuum for Phones, which could be another reason to get these apps in the store.
Even on the latest Redstone Insider build we are not able to download the apps yet, but they can be see in the store at the links below.