It shows off:

• where it takes place (ancient Orr)
• that that place is mostly a wilderness (as the game takes place a thousand years before the first one)
• some playable races (Kodan bears are new, Asura and humans are not, Charr won't be in this one due to the time period)
• different mount types (flying dragon is probably a mount too)
• different modes of movement, which is a large focus of this game
• gliders
• the style they're going for, evolved from GW2

And I've probably missed a ton of things. Once you really start looking at it there's actually a lot going on.