The volley is an offensive shot because it takes a significant amount of time away from your opponent to reload for another groundstroke. When you volley the court distance is cut nearly in half and that means you also have to deal with less time to prepare and execute. The volley really is about deflecting the oncoming ball and in this video I explain the most advantageous and stable positioning of the wrist and shoulder to do so.

The footwork patterns in the previous post are designed to simply get you to the ball and have solid wrist and shoulder positioning. And truth be told if you understand the wrist and shoulder positioning you are after your body will naturally move in a way to allow you to get into that stable positioning quickly. Volley enough and it becomes more like a reflex.