Resolution means the number of pixels, or picture elements, a screen contains. The first number indicates the number of pixels going across the screen from left to right; the second, the number of pixels from the top of the screen to the bottom. A 720p set displays 1024x768, 1280x720, or 1366x768 pixels. A set with 1080p resolution, sometimes advertised as "full HD," displays 1920x1080 pixels. The newest development: The first ultra-high-definition (UHD) models (all LCDs with LED backlighting) recently came on the market. These TVs display 3840x2160 pixels, which is usually described as "4K." That's four times as many pixels as 1080p displays, enabling UHD sets to present even finer detail.
However, resolution alone doesn't determine picture quality. Factors such as brightness, contrast, and color also come into play. What you're watching matters too. To fully exploit the potential of a 1080p TV, you need top-quality high-def content. You can get that from a Blu-ray disc, which contains true 1080p content. A 1080p set will convert HD signal formats (720p and 1080i signals from your cable box, for instance) to match its native screen resolution. If the video quality of the programming is good and the TV does the job well, the picture can be outstanding.
Deciding what size TV to buy is one of the more enjoyable aspects of purchasing a new set. Most consumers tend to go bigger when replacing their old TV, because it enables them to better appreciate the fine, sharp detail of HD content, making it more compelling and creating more of a theater-like experience. If you're replacing an older TV, note that you can't compare the screen size of a conventional squarish tube TV with a widescreen HDTV set because the proportions differ. Stepping up from a 27-inch tube set to a 32-inch–wide screen won't give you an appreciably bigger picture, because the 32-inch screen is wider but not much taller than the 27-inch screen. As a result, "talking heads" on news shows will look about the same size; on the 32-incher you'll just see more of the scenery alongside the people.