The EnTama was released around the same time the V3 was released around the world. The EnTama is a completely differnet and new Tamagotchi.
The outstanding difference is that the Tamagotchi can 'connect' to the internet to something called eTamaGo. eTamaGo is like TamaTown, except it has better and new features, as well as you must have an EnTama to access it.
Other features inculde your Tamagotchi going to school, going to work, cooking and new games and many other features. For a complete list of features, have a read over at the forums.