My main source of research about storytelling/screenwriting/how-to-write-a-book manual is . But, the definition of "beat" given by  maybe can causing me some confusion.
In  we have a definition about what is an event and what is a beat. A event is something which, naively speaking, is both a point of life's character and something that causes change: after an event occurrence the character's life is changed (*). A beat is something that compose an Scene: Events+beats = scenes. A beat is something that catalyzes the conflict (external or internal) between the character and the world. Futhermore a beat is something that gives you a "fine tuning" (i.e. you can add beats to introduce,for example, tension into an not-so-interesting original scene) for the great change of the scene.
But accordingly to source  the author gives us an slightly different point of view of structure: "Stories are divided into Acts, Acts into Sequences, Sequences into Scenes, and Scenes into Beats" And also some youtube channels gives us something similar like videos entitled "The Beat Plot Structure" and so on. With this point of view in mind, is almost like beat and event are synonyms or an event is a more heuristic concept.
So, what is the difference between and Beat and an Event?( In particular on BOOK AND SHORT STORY writing process).
 MCKEE.R. Story. Itbooks, New York, 1997.
(*) Then we have the notion of a Story event: the one which deals specifically with the character and an "trivial event" (or just an event) that do not deals with character (like an cup of glass fell from the top of an table and smashed to the ground).