In a brief overview;
More or less an expansion to the previous game, using an improved game engine, a larger map and generally better everything else... really quite a good game though, the free trial is downloadable from taleworlds.com
the game is the only game which can be considered as a simulator of medieval combat with a totally orignal real time combat system that is skill based. it also accuratly protrays the different cultures, economy, social dynamics and politics within a feudal system.
based in fictional land of Calradia where different kingdoms colide, this is a totally unprecedented free roaming with no forced storyline, you construct your own character and choose your own path through the world to success or failure.
Warband includes a new multiplayer aspect to the series whereby you take part in larger battles that work in a similar way to C&C Renegade (if you know that one).
To be quite frank everyone ive ever known to play this game series has fallen hoplessly in love with it, i urge you to download the trial version.... do it!