From Game Editor
void is a state that a function takes. If a function were to take no arguments then its contents would be void.
int ReturnXY(void) { return(x*y); }
This is a nonspecific way of returning a variable using x and y which are global. One would use void if the function is meant as a start up or deals with globally accessible variables. Functions can also be void. Void functions do not have a return value, as the value is void.
void ChangePos(int x, int move) { actor.x+=move; }
This takes two ints and moves actor accordingly, but the function does not return a value.