More than just a bunch of quick cuts between brief action clips, it's fully narrated, describing the goals of the dev team at Rockstar San Diego and backing them up with in-game footage. Besides just talking up how open the open-world is, it goes into aspects such as the ability to play like a hero or outlaw -- do you bring your bounty back alive or dead? -- and also shows quick glimpses of a variety of cool-looking gameplay, from the old "try to stab the table between your fingers without cutting yourself" to dragging a guy behind your horse on a rope. But, mostly, it just looks so damn cool.
We'll stop with the talking so you can commence with the watching. Giddyup!