A screenplay is like a blueprint for a movie. Unlike a novel, it usually isn't very literary or stylistic. Rather, it sets out the action in very simple, easy to understand terms, and spells out the dialog word for word.
Screenplays must be written in a very exact style, called a format. If they aren't, many agents and production companies won't read them.
Although there is some variation in certain elements of screenplay format, most is very specific. Formatting manually takes a lot of time, and can be very frustrating. Between The Lines handles most formatting automatically, and what still requires your efforts can mostly be done with a single button click.
The sample script pages that load up when you open Between The Lines are a guide that illustrates all the key aspects of screenplay format. Use it as a template, and your own script will be perfectly formatted.