Does a ball that hits the edge of the table count?

It depends which part of the edge it hits.

• The playing surface is the top of the table, including the white lines along its edges (Law 2.1.4). A ball that touches the top edge has touched the court, so it is good.
• The playing surface does not include the vertical sides of the tabletop (Law 2.1.2). A ball that hits only the side of the table has not touched the court, so the player who hit it loses the point.