Here is a video of Steve Jobs announcing the iPad. According to him the device will fill the gap between a smartphone and a laptop device providing a much user-friendly and fun experience to do email, watch videos and photos and surf the web.
Also what makes the iPad so powerful as a consumer device is that it will run all of the 140,000 apps already supported on the iPhone. And the new iBook and iWork app, make the iPad the perfect e-reader and document processor. The video below demonstrates the capability of the device.