Definition of Different Shots

Match on Action Shot

This is when the shot subtly cuts to an object or to look at something from a different angle and then back again without the audience noticing as they would if you were to cut to a different person or setting.

The shot that he original is cut to must show the same action, in the same context and timing so together it looks like one fluid action rather than a sequence of shots that could be film days apart rather than seconds. 

Shot/Reverse Shot

When a character is shown looking at another character off camera, then we are shown the other character's reaction before cutting back to the first character.

Another example of this is a shot of an explosion/villain causing havoc, then cut to the protagonist's reaction and then back to the action aka the villain. 

The 180 Degree Rule

The 180 degree rule is a guideline on where to place the camera to capture to people standing directly opposite them. The camera is placed in a few different places in a circle surrounding the two characters to capture the scene from different angles so the shot can focus on the expression of the character currently speaking or reacting. 

The object of focus must stay in the middle of the shot and the camera must stay on one side of the axis for every shot.