Units of Action, or Units (sometimes also called beats) were first suggested by
Konstantin Stanislavski as a means of helping actors determine the
through line or super objective of a role. A unit is a discrete piece of action in a play-text, marked by a significant change in action. This could be a change in what the characters already onstage are doing or trying to do i.e. a change in their
objective, a new character entering the scene or those already onstage exiting.
See more at Wikipedia.org...