The trailer starts with a lot destruction, showing Ezio’s villa under-siege and being attacked by Templars. Assassin’s Creed: Brotherhood will feature new modes of gameplay, “more memorable moments filled with different experiences”, as is immediately apparent when Ezio’s off horseriding through the city. Ubisoft then announced horseback fighting in the final game. Next, after a canon gameplay sequence, we learn that Ezio will have “multiple new gadgets and machinery at his disposal”, and that at Ubisoft, gameplay diversity is a priority.
Ezio has new moves in the new Assassin's Creed, with more more aggressive combat achieved through new fight mechanics to quickly take care of multiple opponents. He has to strike first, and strike fast. Cesare Borgia, Ezio’s new nemesis, makes his appearance at the end of the trailer, where he kills someone close to Ezio.
A "new order" is needed, and the Brotherhood is formed to get at Rome, the center for corruption...
Also check out the cinematic trailer below, that's no less interesting..