Freeze-dried pieces are nearly water-free, so feeding them dry fills the stomach without hydrating; rehydrated, they resemble the moisture profile of natural prey.
Use warm or cool water rather than boiling water, which hurts texture and some nutrients, and soak to the label's ratio until soft, usually a few minutes.
Once rehydrated it behaves like wet food: do not leave it at room temperature beyond one to two hours, and refrigerate or discard leftovers, sooner in summer.
If the label says treat rather than complete meal, keep portions limited; feeding treat-grade freeze-dried as a staple unbalances the diet.
