Why should you care about HD DVD and Blu-ray Disc? The simple answer is that these two optical disc formats are the best sources of top-quality, high-definition video currently on the market.
How much better than DVD?
High-definition video (usually abbreviated to hi-def, or HD) represents the crème de la crème of visual entertainment in the home. Where standard-definition sources such as DVD deliver their images at a resolution of 720x576 pixels (or 720x480 pixels in the US and Japan), HD resolutions can reach the giddy heights of 1,920x1,080 pixels -- which means they contain roughly four times the amount of detail. HD video also tends to be better encoded and less compressed than standard-definition pictures, which makes colours brighter and artefacts such as noise less visible.
The PlayStation effect
PlayStation 3 has also done wonders for the Blu-ray cause. Prior to its launch in March 2007, HD DVD players had been significantly cheaper than their Blu-ray equivalents. The £425 PS3 changed this, and the fact that it's also a games console makes it a significant Trojan Horse for getting Blu-ray players into living rooms -- you buy it for games but end up using it to watch HD movies too. Or at least that's Sony's hope.
HD DVD hardware is the cheaper of the two, with Microsoft's add-on drive for the Xbox 360 available for a mere £130. You will, however, need a £280 console to plug it into, and it doesn't support lossless surround sound at the moment, so it's not the best option available.