The ART-2 is a type of roller bridge which appears on some models of Ibanez guitars. It is generally used in conjunction with a vibrato to allow the player to effect the pitch of the note in a way that is somewhat similar to a tremolo bridge.
As the name implies it's employed most commonly on hollow-body guitars in the Artcore series but is also found on solid-body guitars with fixed bridges, from the ART series notably.