The word movement in audio production is a loosely used word. I tend to think it means when you apply a certain effect slowly throughout its loop length.
Example – If you have a piano loop, automate a high-cut filter to slowly cut some highs, but then bring them back before the end of the loop. The end result will be a loop that isn’t the same consistency for its whole length.
This movement can be other techniques though, too! Like in this tutorial, I used pitch!