Revent stands, presumably, for 're-event' and is a way of setting up templates on your Windows 10 Mobile device, using Outlook Calendar's APIs. Why use templates? Well, for things you do quite often, for example a club monthly meet-up, a medical check-up, that sort of thing. The idea is that it saves you quite a bit of typing when putting in a new instance of any of these. And it works quite brilliantly. True, it's a commercial utility, at £2, but you can have two templates for free, after which you'll hopefully know whether you'd like to use this more in your busy life.

From the Store listing:

Revent is your handy companion that'll re-invent the way you plan things. Revent will help you create templates for appointments you frequently plan. Open a created template, just fill in the date and select the calendar you wish to use! Revent will do the rest for you. Cortana can even help open templates for you, so you can keep concentrating on your work.

With the easy to use template builder you can set the time the appointment takes, the location with a map and get more productive before you know it!

Here's Revent in action:

So here we go, I'm setting up some new templates, for example this one for an eye test (roughly an annual event), the advantage of the template system is that you can put in far more information in terms of location, reminders, notes and numbers, than you would if putting such an entry in your Calendar as an umpteenth 'one off'; (right) in Revent's interface, here are my templates, just tap any to kick off an Outlook Calendar dialog to create a new timed appointment...

All that's left to do is set the precise date and time, since everything else is already filled in; (right) after doing this, you're prompted to create another appointment - perhaps you're filling in a series of monthly check-ups or meetings?

And here's the new appointment in my Outlook Calendar - job done! (right) in Settings you can set Revent's theme, plus  there's a live tile toggle (though this didn't seem to do anything on my test device).

You can buy this here in the Store for £2 or so. There's also a free trial, thankfully. 

PS. Although not shown here, Revent is not only a UWP app for tablet and desktop too, it also works perfectly on a Continuum display.