If you frequently do team collaboration in your work, there's a good chance you use - or have at least heard of - Slack. The collaboration software has been around for a while now, creating an effective hub for teams that want to collaborate in the most efficient way possible. Now, you can use Slack directly through its own Windows Store app - foregoing the Win32 version.
There really isn't that much difference apart from the Slack app's newfound place in the Windows Store. The app was a direct conversion of the Win32 app, meaning it didn't have to be rebuilt. If you've been using the normal Slack app up to this point, you're going to feel very at home with the new version.
If you're trying to keep together all of your apps inside the Windows Store, the new Slack app is going to be a good option for you. Otherwise, this doesn't have much of an impact. The two versions of Slack should stay identical as far as features are concerned.