What is the difference between differential lock and interaxle differential lock?

Differential lock is a driver controlled locking mechanism which locks the speed differentiation of axle halfshafts in differential mechanisms.After locking, both wheels rotate in same speed.But the interaxle differential(IAD) lockstopsthe speed differentiation of two axles in Tandem axle vehicles by locking the inter axle differential(third differential),after locking IAD both pinions rotate in same speed.