A step outline is a detailed telling of a story with the intention of turning the story into a screenplay

Screenplay

A screenplay or script is a written work that is made especially for a film or television program. Screenplays can be original works or adaptations from existing pieces of writing. In them, the movement, actions, expression, and dialogues of the characters are also narrated...

 for a motion picture.

The step outline briefly details every scene of the screenplay

Screenplay

A screenplay or script is a written work that is made especially for a film or television program. Screenplays can be original works or adaptations from existing pieces of writing. In them, the movement, actions, expression, and dialogues of the characters are also narrated...

's story, and often has indications for dialog and character interactions. The scenes are often numbered for convenience.

It can also be an extremely useful tool for a writer working on a spec script

Spec script

A spec script, also known as a speculative screenplay, is a non-commissioned unsolicited screenplay. It is usually written by a screenwriter who hopes to have the script optioned and eventually purchased by a producer, production company, or studio....

.