High Definition Television is a type of digital broadcasting which allows for higher resolutions than traditional television systems. High definition is currently known in two main forms, either 720p or 1080i/1080p. This number corresponds to the amount of horizontal rows of pixels (alternatively quoted as 720/1080 Vertical pixels by some sources). Standard TVs currently use only 576 horizontal rows of pixels.
The more lines of pixels there are per screen size the higher the resolution, resulting in a higher quality picture. The graphic below shows how resolutions change betwene 720p and 1080i/1080p. Screens using 720p will have a resolution of 1280*720, whereas those with 1080i/1080p will have a resolution of 1920*1080.
If your wondering what the different between 1080i and 1080p is, the 'i' stands for interlaced where the 'p' stands for progressive. Interlaced HDTV runs at just under 30 frames per second, whereas Progressive HDTV runs at a more familiar 24 fps. Although it sounds back to front, the Progressive picture actually runs smoother than the interlaced, and the benefits can be seen when watching fast motion scenes due to the way the technology works.
Ok, so how does this really affect the everyday user? Over the next few years there will begin to be more and more television programmes being broadcast in HDTV, meaning we get to watch all of our favourite programmes with a much higher quality picture. Currently the only way to watch HDTV is to sign up to one of the three services currrently offering HDTV - Sky, Virgin Media or Freesat. More can be read about this on the HDTV Providers information page.
It doesnt just stop there though! No doubt over the last few years you will have heard about Blu-Ray or HD DVD. These are basically high defintion versions of DVD discs. Blue-Ray has now become the industry leader in the high defintion field, and to get the benfits of these new discs, you will need a HDTV Ready TV.
Another area which is now using HDTV technology is the gaming industry. Both the XBox 360 and the Playstation 3 use HDTV. The Playstation 3 also has a built in Blu-Ray player, saving you buying a seperate Blu-Ray player.