A screenwriter is a person who writes the screenplay (or script) for a movie or television show - that is, a screenwriter writes the words that the actors and actresses speak.
A script has all the dialogue of the movie, and will also say things about what it’s supposed to look like but not too much because that the director’s job.
There are certain rules as to how to format a movie script. If these are not followed, then it is highly unlikely that it will ever be taken seriously. In order to test the effectiveness of a script, actors will do a first reading of it. If the format is not clear, then it causes the actors confusion, and makes the task very difficult to complete.
A spec script is a screenplay that a screenwriter writes on his own before even going to a studio and then goes through a lot of changes to become the actual script for a movie. [1]
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