Why do they call a preview the “trailer”?

The wait is over. Available to the world now is the official trailer to When We Went MAD!
A five minute tease, with great bites from Al Jaffee, Al Feldstein, Dick DeBartolo, Duck Edwing, Larry Seigel, Arnie Kogen, Nick Meglin, Sergio Aragones, Frank Jacobs, and Mort Drucker! A true peek behind the scenes of a documentary of ecch-ic proportions!

Click the link above!