Screenwriting, also called scriptwriting, is the art and craft of writing scripts for mass media such as:
It is frequently a freelance profession. [source]
A scene heading is a one-line description of the location and time of day of a scene, also known as a "slugline." It should always be in CAPS.
Example: EXT. WRITERS STORE - DAY reveals that the action takes place outside The Writers Store during the daytime.