Apple Core Storage (sometimes referred to as coreStorage or CoreStorage) maintains a world of virtual disks that can provide the user with flexibility in allocating their hardware.
Core Storage was introduced with Mac OS X 10.7 lion (Build 11A511)
In Apple's Mac OS X Developer Library, there is reference to Core Storage under:
What's New In Mac OS X: Mac OS X v10.7 Lion: BSD And Kernel Features: FileVault
FileVault 2 is not the only application of Core Storage. Core Storage is also used for Time Machine encryption of a backup volume; also applicable without encryption.
Expect more information about coreStorage (the verb) to appear after the diskutil(8) Mac OS X Manual Page is updated for 10.7.