How and what are extremely important to dance for many reasons. I'm going to focus on two important uses: specific movements and communication.
When learning choreography, it is important to understand the distinction between how a movement is done and what movement you are doing. This seems overly simple at first. But as the process continues and movements inevitably change, it is important to recognize when a movement itself changes and when how is movement is done has changed. As a dancer it is important to recognize this because it improves your ability to embody the movement as the choreographer envisions it. We've all been in a situation where a particular movement become very hard because it has evolved over time as the piece takes shape. It is in this situation where you must decide if the movement has changed (whereby you must realize that the movement has a new initiation, a new center of gravity, and a new transition into the following movement) or if the way in which you do the movement has changed (in which case you must simply alter the execution).
As for communication, the relationship between choreographer and dancer becomes much simpler when the choreographer plainly states that they would like to alter the how of a movement or change the movement altogether. This feeds directly into the dancer's abilities outlined above. If you, as a choreographer, clearly state your intention, then half the battle is won for the dancer and you are that much closer to bringing your vision to life and not a subpar version of almost your vision.
