Every time you step near the table tennis table for practice, do you have a specific goal for your practice. If you are training with a coach does he have a plan for the day's practice and more importantly does he share the plan with you?
Purposeful practice is, as the term implies, much more purposeful, thoughtful, and focused than this sort of naive practice. In particular, it has the following characteristics: Purposeful practice has well-defined, specific goals.
I have seen some coaches come to practice and randomly assign drills for students to practice, even if the coach has a plan if he does not share the purpose with the student, she might not understand what the focus is and this goes against well-defined goals as the focus of the coach, and the trainee might be different.