Shot reverse shot, match on action and 180 degree rule

Shot reverse shot
This is a film technique where one character is shown looking at another character, and the other character is shown looking back at the first character. This technique is usually used in conversations or when characters are simply looking at eachother. 

Example:

Match on action
This is an editing technique for continuity editing in which one shot cuts to another shot portraying the action of the subject in the first shot. This technique creates a sense of continuity - the action carrying through creates a "visual bridge".

Example: 

180 degree rule
This rule enforces continuity of the film. The rule states that the camera(s) should remain the same side of the imaginary line. The line is drawn perpendicular to the camera's viewpoint in the establishing shot of the scene. The rule should never be broken, as it confuses the audience especially in scenes of chase, conversation or sport.

Example: