The section under the binding that grips when you kick — via kick wax, scales or a skin. Skating skis have none, so kick wax simply doesn't apply there.
The kick zone is why a classic ski grips at all instead of sliding backwards: you press it into the snow as you kick, and it lifts clear as you glide. On waxable skis the kick wax decides what happens there — rule of thumb: hard wax for cold, dry conditions below about −1 °C, klister for warmer, wet or already thawing snow. The most common mistake is waxing to the air temperature: wax that's too warm slips through, wax that's too cold won't grip — snow temperature is the reference. What often gets missed: slipping is just as often a technique issue, because without a full weight shift the kick zone never gets any pressure. And in competition, fluorinated waxes have been banned at FIS and IBU events since the 2023/24 season.