They must be having skates hidden under the long dress.

As one of the commenters posted, Roombas.

No, actually: “The idea of dancing is for the audience to see the moves, but with Beriozka things are a little bit different. In this traditional Russian dance, performers appear to be floating across the stage, and it is nothing short of impressive. Their secret technique is called the floating step. It seems like these dancers are standing still while the stage beneath them seems to be moving. Even the skirts doesn’t seem to ruffle, but that is all part of the show. The women actually have to stay on their tippy toes (en pointe) the entire time to maintain the illusion.”

There is the merest of side-stepping evidence in the skirts starting around 1:40 but at the same time their heads and shoulders are floating smoothly… such a strange talent !

A lot of very tiny, very rapid steps close together while keeping the upper body level and steady. You can try it yourself and just get a little bit of a sense of what they must be doing, even without the finesse that would come with tons of practice. Yes, it does look as if they were on wheels. I’ve seen this in a number of performances of Russian dance, usually done by men in long robes.