For me, the job of an actor is simply to use text to get an emotional response from an audience.
An actor works to get underneath the skin of the text; to understand the character, their history, what motivates them, their relationship to other characters and how their current situation affects them. It’s essentially a forensic psychological analysis of the character, creating parts that are needed but not obvious from the text. This is what makes different performances intriguing to watch.
From this understanding, the actor will imaginatively bring those characteristics within their own, to create a new, completely authentic character whose every action is true to both life and the written character.
A performed character may well have certain physical characteristics or “tics” that inform the audience of the underlying psychology. Think of Aragorn in The Lord of The Rings, spending much of his time looking down as a mark of his uncertainty, until he is sure of a situation (usually confronting an enemy) when he looks directly forward. Consider the connection between Harry Potter and Voldermort indicated by their head-circling habit.
The actor will then put the character into the given circumstance of the text. The audience will “buy in”, understand and, if it’s done well, react emotionally to the performance. Job done.