What is Blocking?
Blocking is the process of planning and rehearsing the movements, positions and actions of the actors within a scene. Whilst a scene can and should be dynamic, there also needs to be a level of structure.
In theatre, the lighting is fixed within the tech rehearsals, therefore the actor needs to hit their marks to ensure they’re well lit. Similarly, whilst film’s often use steadicams and camera movement, the camera is often fixed based on the blocking of the scene, especially when using tracks. Therefore the actor needs to hit their marks for proper framing.
On sets, this is done by adding bright “marks” on the floor that are placed during the walkthrough to allow the actor to know exactly where they need to stand at certain points within the scene.