This is an excerpt from Tennis Skills & Drills by Joey Rive & Scott Williams.
Points of Contact and Strike Zones
Players should know the correct contact point and strike zone for the shots they want to execute. Their court position, movement, and racket preparation should match that contact point. Three points of contact are possible: attack, rally, and defensive. They fall in a horizontal plane (see figure 1.13). Although players must address each individual ball in a groundstroke, the style of play sets the tone for the types of shots they want to execute.