MacGuffins

A MacGuffin (sometimes McGuffin) is "a plot element that catches the viewers' attention or drives the plot of a work of fiction."

Sometimes, the specific nature of the MacGuffin is not important to the plot such that anything that serves as a motivation serves its purpose. The MacGuffin can sometimes be ambiguous, completely undefined, generic or left open to interpretation.

The MacGuffin is common in films, especially thrillers. Commonly, though not always, the MacGuffin is the central focus of the film in the first act, and later declines in importance as the struggles and motivations of characters play out. Sometimes the MacGuffin is all but forgotten by the end of the film.