In the lead-up to the iPad 2 announcement, many were predicting that Apple would give the tablet's 9.7-inch screen a bump in resolution. But when Steve Jobs revealed the second-generation iPad to the world, it had the same pixel count as the first one: 1,024x768, even though the display was revamped to be considerably thinner. Why no extra pixels?
Looking at the history of the display on the iPhone offers some clues. Apple kept the display of the iPhone at the same 480x320-pixel resolution for the first three versions of the phone, and when it finally upgraded the display for the iPhone 4, the bump was huge, doubling the display resolution to 960x640 pixels. The upgrade also introduced the term "retina display," a piece of marketing jargon that Apple doesn't quantify, but generally means a display that is better than the limits of human vision.