Games in SD Card Root?

In several web pages ive seen that some guys are saying that the games have to be installed in the SD Card Root to be played or something like that...... for example a guy who said that a "x" phone has to be rooted therefore the game its installed from the root...... so i wanna know why, im asking this ´cause the last week ive installed a game from the sd card (not the root) and after ive played the game my screen fail and it went dark.... (it was about the ilumination in the screen... i repaired my cell after that) so the question its also if there´s some kind of connection ´cause i think my screen didn´t put up with the game...... please anybody know the answer?