Continuity editing

180 degree rule
This is when two characters in the same scene should always stay in the same place / relationship to each other, e.g.  if one character is on the left of the shot he should stay on the left through out the scene while the other stays on the right.

Match on action
this is when a cross cutting of shots in different locations that are occurring at the same time are being shown simultaneously. parallel editing is used to help create this effect.

Shot reverse shot
this is when one character1 is shown looking at  character2 usually over his shoulder. this is then reversed showing the character2 looking at character1. this creates a illusion of conversation and the viewer gets both sides of the story.