For almost as long as there have been feature movies, there have be previews of forthcoming movies, intended to lure audiences in to see those features. Studios, major and minor, had departments that made those previews.
With the deconstruction of the studios in the 1950s and 1960s, that task fell largely in abeyance. So what did releasing comings like MGM do with a major production? They produced a short movie that lured the audience behind the screen, told them who would be in it, and so forth. Instead of a one-minute notice, audiences got a taste of what was to come.
This is one of them, touting the cast, the difficulty of making the picture, and finally an action sequence, complete with a score to raise ones anticipation.