As far as I know, a ground ball is not a type of ball or a game, but rather a type of hit in baseball, where the batter hits the ball and it rolls or bounces along the ground (within bounds). This is also called a "grounder". The term may also be used in lacrosse, but that's not a very popular sport in America, so most Americans would just think of the baseball-related meaning.

Hello Shana, A "ground ball" (grammatically it is correct to write these two words separately) is a baseball (also called softball) which one of the players (called a batter) should hit with a wooden bat.

I guess you and I will have to agree to disagree. I would however advise the student to trust the native speaker who has played baseball.

It is describing the moving baseball. If it was hit so that it is just above the grass or is even rolling on the grass, it would be called a groundball.

‘ground ball’ can refer to both the hit and the ball. (Also, it must hit the ground - being close to the ground doesn’t qualify.) And to make matters even more fun, not all balls that hit the ground qualify as ‘ground balls’. Example The batter hit a ground ball to short. (The hit) The shortstop cleanly fielded the ground ball to start the double play. (The ball. The ball that was hit on the ground by the batter. Once he’s fielded it, it isn’t a ground ball any more - just a ball)