In Night, when Elie's mother and sister moved to the right, they were going through the process of selection. Selection was the process by which the Nazi's determined who was healthy enough to work and who was not. The Jews went through selection many times. When Elie's mother and sister moved to the right, they were being separated by male and female and were sent to different concentration camps.
It is also significant to note that when they moved to the right, it was the last time Elie saw his mother and sister. At the moment he does not place importance on the event since he was not cognizant of the fact that he would never see them again. This serves as a demonstration of how seemingly mundane events can change the course of a life.
Where was the last place Elie saw his mother and sisters?