Blocking is a term inherited from live theater to describe an actor's movements on stage. Your ideas about blocking a scene will have a big impact on camera placement and other elements of your shot plan.
BLOCKING: An actor's movements within a scene.
Naturally, you want to limit the actors' movements so they won't stray beyond the boundaries of the set or move into areas that would be out of focus or poorly lit. At the same time, effective blocking is every bit as important—sometimes more so—than dialogue in conveying information and emotion to the audience.
Screenwriting instructors talk about the notion of “character” ...