iPad Apps "Cleaning"?

Have you ever noticed "cleaning" under some of your apps, like Facebook, on your iOS device?  It can happen quickly and unnoticed, because I just noticed it for the first time this morning, so I searched for an answer online.

I found an article from iMore.  The article was written back in Dec of 2011 and its perspective is in iOS 5 (iOS 6 is our latest update), however Rene Ritchie's explanation is helpful and to the point.

Check out the article here.