Chick 1 says:

What do the Ark of the Covenant, the Maltese Falcon, and Unobtanium all have in common?  They are all versions of the MacGuffin, one of the most commonly used tropes of all time.  The MacGuffin is simply what they are after; what the hero is chasing, trying to find, or trying to protect.

The MacGuffin has been a trope in stories for as long as there have been stories (see the Golden Fleece in Jason and the Argonauts) but it was first given its name by Alfred Hitchcock who credited one of his screenwriters with the term.  The MacGuffin is the external motivation for the hero’s journey but has little to do with the hero’s actual character arc.  In its purest form, the MacGuffin could be replaced with any other item and the story would remain essentially the same. Read more