A grip strap has a textured or rubberized interior surface that physically grabs your boot shell instead of just pressing against it. This keeps your boot from shifting or lifting inside the binding, especially during aggressive turns, choppy snow, or big drops.
The real benefit is that you get a more secure hold with less ratchet tension. Instead of cranking the strap down until your foot goes numb, the grip surface does the work—meaning fewer pressure points and better comfort over a full day of riding.
Grip straps are most popular with freeride and aggressive all-mountain riders who need their boots locked in at speed. If you mostly cruise groomers or lap the park, a standard padded or asymmetrical strap may feel more comfortable and forgiving. But if you've ever noticed your boot slipping mid-turn or had to overtighten your straps to feel secure, a grip strap is absolutely worth the upgrade.