Full HD, or full high definition, is the highest picture quality available on a consumer television. There are three different HD modes: 720p, 1080i and 1080p, but only 1080p is full high definition. The number part of 1080p refers to the number of vertical lines displayed on the screen—the higher the number of lines, the sharper the picture. The "p" means that the screen uses a progressive scan to display images. Progressive scans display images very quickly by completely refreshing the screen with every frame. This allows quick movements to display in sharp detail.
In order to understand why 1080p is considered full HD, it is important to know a little about the other display options. Most standard definition TVs are 480i resolution. That means they have 480 lines of vertical resolution and an interlaced scan display. Interlaced scans refresh the screen half of the lines at a time, first the even lines then the odd lines. This means that for each frame displayed, only half of the lines are new, the other half are from the frame before. The next common resolution is 720p which is both an increase in resolution and an improvement in scan style. 1080i was the next step with an improvement in resolution, but a step backward in scan type. Lastly, the 1080p has both the full resolution and progressive scanning.
Only equipment that is designed to run in 1080p creates full HD material. Many low- to mid-range cameras, video recorders and televisions say they are able to display in 1080p, but that isn't exactly true. What these items do is create, read or display materials in a lower resolution or with an interlaced scan and upscale the video to 1080p. The scaled-up result is close to 1080p, but not quite there. The image will stutter a bit, fast motion will blur or certain areas of the screen will appear fuzzy as if they aren't in focus. In many cases, anything designed to run in full HD will have have a label listing 1080p native somewhere on its packaging.
There many full HD options available, but most over-the-air TV broadcasts are still in 720p or 1080i. Many satellite and cable providers, however, have moved up to 1080p. The number of televisions, computer monitors, video cameras and DVRs that are native 1080p continues to increase. Many video gaming systems are able to display at full HD as well, and some also can play movies in HD format.