The figure starts in a circle:

    4
2       6

1       5
    3

Bars 1-2: The “first triangle” (dancers #1, #4 and #5) dance clockwise to the next first-triangle position, with all three dancers clashing with each other in the center as they pass through.
Bars 3-4: The “second triangle” (dancers #2, #3 and #6) dance clockwise to the next second-triangle position, with all three dancers clashing with each other in the center as they pass through.

Repeat.

At the end of the figure, the set has now rotated into the following configuration:

    5
6       3

4       1
    2

All dancers have shifted one position counterclockwise within their own triangle. (Alternatively, you can think of it as the entire set of six having rotated two positions counterclockwise.)