Macguffin

Macguffin is a plot element that catches the viewers' attention or drives the plot of a work of fiction". The defining aspect of a MacGuffin is that the major players in the story are  willing to do and sacrifice almost anything to obtain it, regardless of what the MacGuffin actually is. In fact, the specific nature of the MacGuffin may be ambiguous, undefined, generic, left open to interpretation or otherwise completely unimportant to the plot. Common examples are money, victory, glory, survival, a source of power, or a potential threat, or it may simply be something entirely unexplained.

Macguffins are commonly used in thrillers, for example in North by northwest the macguffin was some  potential threat to the enemy, but no one cared about the macguffin all we cared about was if Roger Thornhill survived and if the villians would get our hero and if our hero will rescue his damsel in distress.