When closing a foreround activity that is on top of the wallpaper when the previous activity is also on top of the wallpaper, this is the animation that is run on the previous activity (which is entering the screen). The wallpaper remains static behind the animation.

Must be a reference to another resource, in the form "@[+][package:]type:name" or to a theme attribute in the form "?[package:][type:]name".

[Android Documentation]