iPad has five different models to date. These include the iPad Mini, which has a 7.9 inch display screen and Siri. The iPad 4 has the Retina Display screen and is also Siri capable. What should be the iPad 3 isn’t called the iPad 3 because it came out shortly before the iPad 4 and doesn’t have the Retina Display option, although it is identical other than this screen type. The iPad 2 is considered an entry level iPad, as the original iPad is as well. The difference between the iPad 2 and the original iPad is the iPad 2 has two cameras in order to support FaceTime video chats.
Resource: Small Business Chron