The Three Rules of Continuity:

Match on Action - this is where there is one smooth movement through more than one shot, portraying the action of the subject in the first shot. This creates the impression of a sense of continuity. Also, the action carrying through draws the viewer's attention away from slight cutting.

Shot-Reverse Shot - this shot is usually used in a dialogue between two characters of whom are looking at each other or an object. For example, a shot that shows what the certain character is supposedly looking at (either a point of view or over the shoulder shot) and then is followed by a reverse angle shot of the character themselves look at the object, or looking back at the other character.

The 180' Rule -  this is where filming only takes place at an 180' angle. For example, there is a medium shot of a dialogue between two people, and character number one is on the left, however, character number two is on the right. The camera work is allowed to change, but character one must remain on the the left, and character two must remain on the right. If the camera 'crosses the line' and films character one on the on the right and character two on the left, the rule is broken.