In cinematography, composition refers to the frame of the image and how the elements of the mise-en-scène appear in it. Composition guidelines must be observed when telling stories visually, as in filmmaking.
If a character is looking frame left, then he should be positioned frame right. This makes the framing comfortable because the subject is looking at the open space in front of him. This open space is called lead room or lead space.
If the actors were frame left, looking frame left, then the empty space would be behind them. This doesn’t feel right because they would be looking at the edge of the frame. The proximity to the frame would generate a claustrophobic undertone that could disconcert some viewers.
You may have notice in other movies that when two shots of two actors in different sides of the screen are cut together, the audience surmises that the actors are looking at one another, regardless of where they are.
Rule of Thirds
Another basic composition notion is the Rule of Thirds. To follow it, you have to imagine the frame with two vertical lines and two horizontal lines, thus creating three vertical sections of the same dimensions and three vertical sections also of the same size. The result is something like this:
The intersections of the lines are points of interest, where important objects are placed in the screen. These points of interest are comfortable to the eye, thus the middle portion of the frame are sometimes kept “empty” or clear.