Stand height (also called stack height) is the distance from the top of your ski to the bottom of your boot sole once the binding is mounted. It determines how high you're lifted off the snow surface.
A lower stand height—around 15-20mm—keeps you closer to the ski, giving you better snow feel and a more stable, grounded ride. Freeskiers and powder skiers tend to prefer this. A higher stand height—25mm and up—gives you more leverage over your edges, which translates to stronger, snappier carves. Racers often go 30mm or higher using lifters under their bindings.
For most all-mountain skiers, the sweet spot is 17-22mm. Don't assume higher is always better—too much lift raises your center of gravity and can feel twitchy, especially in soft or variable snow. Choose based on how and where you actually ski.