The idea is to keep your phone camera steady while snapping something with Refocus - it then grabs a number of shots at different focus points, storing them in a special 'RFI' object that can be shared with other Refocus users if needed. Or, more immediately, you'd typically step forward and back through the shots taken and save the one for which the subject you want is best focussed. You can also tap on the subject and Refocus will try and work out which shot is best for you.
Here's Refocus in action:
Having taken this scene with extremes of foreground and background detail, here it is in Refocus after tapping on the background/distance...
...and tapping on the foreground object gives a very different photo. Very cool. Note the 'save' icon for saving a just-captured image to the phone's Camera Roll.
Another example, helpfully supplied as part of the Refocus install, here after tapping on the background dried grass...
... and after tapping on the foreground wood. Note that opening up a previously taken Refocus 'image'/object doesn't give you a 'save' icon, somewhat oddly, but you can use the menu to share an image by email (e.g. to yourself!) or via social networks as usual.
There are is one caveat worth noting, mind you. Refocus is limited to 1 megapixel images, which is disappointing on a modern smartphone with 8 megapixel camera and 1GB of RAM (in the Lumia 920's case here). Fine for social network sharing, but you wouldn't want to use the application for any precious scenes - Refocus is more of a tech demo and for fun use.
Hopefully Refocus can be updated to support at least 3 megapixel images at some point in the future, which will make it much more appealing to shutterbugs.
You can grab Refocus for trial or to buy for 79p here in the Windows Phone Store.