The transition is the part between turns, when you are transferring from one set of edges to the other set of edges. The components of the transition are releasing the edges from the previous turn, the transfer - where balance (weight) is transferred between skis and you are going through "skis flat" and on to the new set of edges - the "edge change", followed by the engagement of the new edge.
The determining factor is how you released the previous turn. In a good transition, you are floating, with the skis carrying minimal weight but still in contact with the snow - although a number of transitions do not use contact.
Here we'll look at some important elements of the transfer:
The default transition is one with a clean edge change - in a clean carving transition, we avoid pivoting the skis, which have a tendency to twist and change direction when flat on snow, especially when coiling properly from the previous turn, as the stored coiling tension throughout the body tends to leverage the upper body's inertia and twist the much lighter lower body, boots and skis.
A smooth and continuous edge change is great, like in these windshield wipers turns:
Although this should be our "go-to" transition, if a clean edge change is not in the cards, we talk about redirection transition and it can be a stivot, a step or even a stem.
When a clean edge change is not possible, due to various reasons, we are dealing with a redirection. There are a few ways to redirect the skis, from full-on stivots, to pivoting and steering a light ski, to the GS step++ etc.
We transfer weight not only from edge to edge, but also from ski to ski namely from the old outside ski to the new outside ski. We should try to avoid an abrupt weight transfer, i.e. a "hop" from the old ski to the new ski and focus on a smooth weight transfer, using a lot of relaxation and Flex to release.
See Flex to transfer weight as a good session to start working on the weight transfer.
The other important thing to do in transition is to get forward again, to recenter and pull the skis back under the hips, so you start the next turn carving, with pressure on the tips - see the first few frames below, where you can see how the boots are pulled back and kept under the hips through transition and even as the outside leg extends:
If you feel the back of your boots in transition, you need to pull back harder on the boots - try to feel the shins pressing in the tongues of the boots, that's a sure sign that the boots are as far back under the hips as they can be. Later, as you extend to the side, that tension will keep them right under the hips, so you can apply pressure wherever you need on the ski (the tips to start the carve) and that's expert-skiing++.
If the previous turn was done right and you managed to extract good energy from it and are now floating through transition, everything is perfect and set in motion by the release of the previous turn.
If the previous turn was not that great, or the release mistimed, then you have some work to do to recenter and get the hips ahead of the boots, for the new turn.
The float is not as much a technique as a place between turns where time stands still.Anyone Can Be An Expert Skier 2, p87, Harald Harb, 2001
The other thing you will notice on the photo above is coiling in the first few frames, (separation, counter) where the shoulders point more down the hill while the skis transition to the side. This is another sign of expert-skiing and usually more pronounced in shorter turns.
In fact, from top to bottom, while the skis turned more than 90 degrees, the shoulders barely turned maybe 20-30 degrees.
At the expert level:
Here's another view on transitions, more race-oriented: