The Tagline is a memorable one-sentence advertising catchphrase created to stimulate interest in a film. A masterful tagline will set the precedent of the film in such a fashion that it will jump out of the advertisement and spark a word-of-mouth campaign so dear to a studio's heart....and bottomline.
The Tagline almost always sits directly below the title of the film on marketing materials such as movie posters, handbills, and periodical splashes.
The Night He Came Home! - Halloween
Long ago in a galaxy far, far away. - Star Wars
The truth is out there. - The X-Files
Houston, we have a problem. - Apollo 13