If a player who is in possession, i.e. was holding the ball, goes to ground he may punch/slap/push the ball while it is on the ground. He may not pick it up or grab it.
I'm not 100% sure of it but I assume he can score a goal by doing this but its not something I've ever seen yet.
Like I've already said alot of refs don't even know the rule. I once came across a ref who penalised a team-mate for slapping the ball on the ground like that. When challenged the ref said 'you can only do that if you are in physical danger' !!! He didn't have a clue, we actually laughed at him which made the thick fu*ker even thicker!