There's a lot of discussion around pivoting and around the technique of the stivot or the stivie sometimes seen on the World Cup, which Ted Ligety explains it the best as something you have to do on the steeps to control speed.
We're left though with the question of the pivot: should we forcefully pivot the skis or not?
Since many confuse stivoting with pivoting, let's clear that up first: stivoting is a technique often seen in racing on a steep pitch, where the skier is coming in too fast and cannot make the turn on the line he or she would want. The skier will throw the skis sideways and drift them to a point where he (or she) slowed down enough and is back on the desired line, will let the ski engage at that point and continue a carved turn.
The main advantage of it is controlling the speed on the steeps, in fact Ted Ligety explains this best as something you have to do on the steeps to control speed. Otherwise, racers prefer to carve their turns, see Training the ideal line.
On the other hand, pivoting is a forceful (active) rotation of the feet (i.e. skis) around their vertical axis. This can occur with or without the legs rotating in their hip sockets (depending on knee flexion) although the most common is with a flat ski and long legs and is in direct opposition from carving, where the snow makes the ski turn (i.e. the ski bends and that makes it turn).
The oversteering is a more general concept: the skis, when put on a given edge angle at a given speed, would like to turn with a certain radius, given by their design and shape. Oversteering refers to getting the skis to turn faster than this "natural" radius.
There are several mechanisms to control oversteering:
Finally, there is another concept, that of redirecting the skis - this is seen often in racing, when the skis are light and the racer allows them to change direction while unloaded and tipped to high edge angles, in transition - while related to both, this is neither pivoting a flat ski nor drifting to dump speed.
We've clarified all these terms before getting into the meat of this article, so we don't confuse oversteering with pivoting with redirecting with stivoting - as you can see, these are different concepts, with different tactics and different biomechanics.
You can read the entire argument below, but the crux of it is that there are 2 basic ways to turn the skis: forcefully pivot and turn them in the direction you want them or, use the ski design: put the skis on edge and manage pressure and angles to get them to turn, with minimum active rotation of the ski.
While there may be a lot of blending possible in between these two extremes (generally referred to as "steering"), we consider the brute force twisting of the skis as to be avoided in general and we prefer to focus on convincing the skis to turn - this is the more skillful approach. By avoiding artificial rotations and focusing practice on this other end of the spectrum, we can reach much better performance and overall balance and ski control skills.
I drive both street bikes and dirt bikes, so I have no problem understanding carving/traction and drifting/lack of traction.
First, carving: there are a few ways to get a motorcycle to turn and the best by far is to work the handlebars by counter steering, to lean it into the turn and then it turns due to its design. Turning action controlled with handlebar pressure and finessed with peg pressure and body positioning. Likewise on skis, the best by far is tipping the skis on edge from the ankles and managing pressure/edging to determine turning. No drifting involved in this maneuver, whatsoever.
Need to turn more? Lean the bike into the turn more or tip the skis on edge more!
Now drifting. First of all, why do we drift? It allows us to take a tighter turn radius, at a given speed, at a given TRACTION LEVEL, by pointing the bike quicker the other way.
To get a dirt bike to drift, you do one of two things, generally: power slide or brake slide. You break traction at the rear wheel via either giving it too much power or locking it with the brakes. The mechanism for both is identical:
Then the drift is controlled with body, throttle and brakes. The same thing can be done with your car, if you're blessed with rear wheel drive or you hacked the parking brakes to work on the rear wheels only.
Those who use a mountain bike will have no problem understanding the concept, except maybe for the power slide - same thing as the brake slide, except more controllable.
On skis, I can drift the tails, without any rotation movements whatsoever, just pressure (fore/aft and flex/extend) and edging management (i.e. reduced edging so they don't grip). This is what I would call a finessed drift. It is what most high performance skiers to at the top of the turn, when they need to, including all of World Cup, sometimes referred to as steering.
So, while going across the hill, you put the skis on edge slightly, not enough to grip and carve, and they will start to drift and turn. If you come through a deep retraction and extend the leg(s) the other side, again they may drift and point down the hill, especially as the boots keep them at 90 degrees to the feet, which are to the side.
The opposite of this is the forceful pivoting of the skis, which no longer fits the description of drifting, as you pivot/rotate the skis forcefully, i.e. without using edging and pressure management to drift them. This is the one that reduces control, as any forceful action automatically creates extra momentum that has to then be managed. Commonly referred to as pivoting.
The equivalent of this in a car is, say in a forward wheel drive car without rear brakes, a forceful application of steering, at speed, to force a momentum and rotate the entire car, overpowering the traction and causing it to pivot. This is the more uncontrollable of all drifts, since you are lacking the controls to manage it: you have no rear brakes and no rear power to manage the drift. Once you break traction, it is consumed, the momentum of the initial pivot is done and so is control. It is very hard to drift a front-wheel drive car without hand brakes on the rear!
On skis, after you forcefully pivoted them around, you can however continue to use edging and pressure and continue a controlled drift. However, the forcefulness aspect of it reduced control at the beginning and usually results in a fuzzy outcome.
Does that make sense? Surely the parallel has been drawn before... does that clarify the difference between the two ways to start the drift? Does this parallel emphasize why one is more controllable and one less controllable?
I think as coaches we are often guilty of encouraging pivoting at the same time we say not to... by, for instance, over-using drills picket fences and erring on the side of a flush too tight or a set too tight for the skill level. I think we should instead use more environments that encourage proper ski management: edging and pressure. Skiing in balance is always better, see Training the ideal line.
We manage pressure fore/aft as well as via extension as well as muscle activation, learn more via Intro to pressure.