WTR (Walk to Ride) was Salomon and Atomic's walkable sole standard, but it's been largely replaced by GripWalk in newer equipment. If your boots have WTR soles, they'll work in bindings specifically marked as WTR-compatible, and many GripWalk-certified bindings also accept WTR soles—but not all of them, so you need to check the binding's compatibility list carefully.
The key thing to watch for is mixing WTR boots with standard alpine (ISO 5355) bindings that aren't designed for walkable soles. The rockered WTR sole shape can cause unpredictable release behavior in those bindings, which is a real safety concern.
If you're shopping for new bindings and want to keep your WTR boots, look for models that explicitly list WTR compatibility. If you're upgrading boots down the road, GripWalk is now the dominant walkable-sole standard and gives you more binding options going forward.