Turning on the edge without sideways slip — the ski or board carves a clean line into the snow.
In carving the ski's sidecut does the work: tip it on edge and load it, and it bends into an arc and turns by itself — you don't steer, you edge and apply pressure. You can see it in the track: two narrow lines rather than broad skidded patches. Speed is a prerequisite: too slow and the edge doesn't bite, so the ski slips. The most common error is sitting back — lean backwards and you unload the tip, losing exactly the part of the edge that initiates the turn. The second is rotating from the upper body instead of edging from the legs. On hard, icy pistes carving also needs well-sharpened edges, or no amount of technique will hold.