SBIcon is a class representing an icon displayed by SpringBoard. It is not typically used directly; instead, its various subclasses are used: SBApplicationIcon, SBBookmarkIcon, SBDownloadingIcon, and SBDestinationHole (which is a blank space used when rearranging icons).
In iOS 5 Apple split up SBIcon, creating a separate class for SBIconView, and just leaving SBIcon with behind the scenes stuff.
Launching an Application using SBIcon
0 = Springboard/dock 4 = Spotlight