Shot Reverse Shot Rule

Shot Reverse Shot, is a continuity editing technique used when filming conversations or to show characters looking at objects/each other. For example, a shot showing what the character is looking at is then followed by a reverse angle shot of the character actually looking at it or of another character looking back at their reaction. This technique is often used alongside the 180° in order to prevent confusion for the viewer.
The picture below is an example of shot reverse shot: