The iPad is a tablet multimedia device, whereas the Nook is an eBook reader. The iPad is run by the iOS, while the Nook is run by android. The iPad software is exclusive to the iPad, while Nook software is not. Applications may be installed on the iPad, but not on the Nook.
The iPad uses a single large screen while Nook utilizes two kinds of smaller screens. iPad is used to play games, read documents, watch movies, and an assortment of other endeavors. With the iPad, you can download and connect software from the Apple App store, which raises its potential uses. With Nook, you can only download new eBooks to read. The iPad uses a large touchscreen LCD, which is also an input device. The Nook uses a smaller e ink display that enhances battery life while reducing strain on the eyes during reading.