The skip is the brother to the vanish and should be understood to be possible any time a vanish is. Skips are simply vanishes where both feet are never in contact with the floor at the same time. For this reason, they can also be viewed as a series of singular transitions. One way to understand this is to think of skips as a missleg into a swingthrough, or a swingthrough into a carrythrough, a carrythrough into a missleg, etc. By thinking in terms of compound transitions, more possibilities can be realized simply by substituting the singular transition on each foot for another.
The skip is a powerful transition because it can be used to manipulate stance and takeoff, as well as create a number of possible rhythmic changes to a combination. It is this flexibility, as well as the technical difficulty that often accompanies it, that makes the skip so special.