A script is a written document. It is mainly used to plan TV shows, films, plays etc where they are used by actors to learn their lines for the scenes, and by other professionals - camera operators, lighting crew, sound technicians etc to know what is meant to be happening in that scene.
Scripts can also be used to help plan comics, voice overs, computer games and animations.
They can be an original story, or an adaption of a book or something similar.
A script should contain:
- Set or location of the scene
- Character names
- Character dialogue
- Dialogue direction - volume, emotion to put in the lines etc.
- Direction - what happens in the scene eg Dave walks towards the fountain, ducks down as a pigeon flies in...
- Shot types (for the cameras)
- Camera Movement
- Sounds (for example a Voice Over (V.O.)
- Special Effects - such as an explosion or a caption (called chyron)
Script for Arrested Development (created by Mitchell Hurwitz)
There are some Formatting rules that you have to follow with a script (Screenplay format):
- Locations are always in Capital Letters. INT. shows it's inside (interior) EXT. means outside (exterior)
- Character names are always in Capital Letters
- For Dialogue, Character Names should be 3.7 inches from left edge, 2.2 inches from left margin
- Character Dialogue is 2.5 inches from left edge, 1.5 inches from left margin
- Font is Courier, size 12
- Page Margins: Left - 1.5 inches, top, bottom and right - 1 inch
- Pages numbered top right as 1. The Title Page is not numbered and you don't show the number on the first page.
To see more detail, take a look at this screenplay format pdf by Matt Carless (via BBC writersroom)