Sometimes on a steep pitch, a racer cannot carve a clean arc and needs to reduce speed or modify the arc and in this case one of the techniques used is the stivot.
Stivots sacrifice the top of the turn to allow carving the bottom of the turn and get a good line.
There are a few flavours between stivot and redirection++ but in general, the skier releases from the previous turn, unweighting and redirecting the skis to point down, slides on the skis sideways until past the gate and then sets the edges in and makes the turn.
The ski can be redirected by a forceful rotation/pivoting and small angles or by a tipping and lateral extension or other means. The skidding is used to reduce speed, which tends to pick up fast on a steep pitch.
While skidding sideways at the top of the turn, the angle of the ski is increased as well, so that, in conjunction to reducing the speed, the skis will grab an edge eventually and carve out the rest of the turn.
This is not the "go to" racing technique, but used on exception. Listen to the differences here:
Racers (and skiers in general) need to carve through the bottom of the turn, to have a platform and deflect the body across the slope, see Impulse. Carving the top of the turn and especially the speed at which a skier can carve the top of a given turn corresponds to a higher level skill.
In coaching racers, I emphasize that when free-skiing they must never reduce speed by a skidding action of their skis. Every time they do this they reinforce muscular habits related to skidding turns. How The Racers Ski, Warren Witherrel
Here's Ted's thoughts on it: