The update is currently available only for selected Xbox One preview members, although access will gradually be extended to more users before the final release.
The Windows 10 OS update for the Xbox One has already been announced and implemented several months prior to this announcement, which subsequently opened the game console's compatibility with Universal Windows Platform (UWP) apps.
This update, however, is the very first time that any Universal Windows App was implemented for the console.
As for the app itself, the Blu-ray player will now replace the old native Xbox One Blu-ray player app. Interface changes are technically non-existent. In fact, there's actually no directly discernable visual changes.
Apart from its coding, it would technically (by definition) be the same as other Blu-ray players on other Windows 10 machines, run by the console's own version of Windows 10.
Xbox One's very first UWP app is the first of the many UWP apps that are to come very soon for the console. No new similar updates will be available for a short while, but expect a flood of them to come after Microsoft's upcoming major Anniversary update.