This is yet another camera technique that aims to create verisimilitude. Following the 180 rule a person can be shown walking from the left side of the camera to the right side. When they reach the right side the camera cunts to another scene so the person is now back on the left side of the shot and walking to the right again. Shown below.
This camera technique is not only used for walking, it can be used to voom in and out to show what someones doing or flicking to the other side of a door when someones opening it.