One glorious feature of the XBox 360 is that it can put out a high definition TV signal. All of us players with HDTV systems will get to see amazing clarity.
First, it's important to comment that the XBox 360 has two separate cables that it can use. One puts out the high quality HD signal. The other cable is the STANDARD TV signal that we know and love from existing game systems. So if you don't have a HD TV yet, don't panic. As long as you get the standard cable, you will be able to play the system on your standard TV.
That being said, it's important to note that the games will look FAR better on a HDTV, because of course the HDTV has a far better resolution. Here's how TV resolution works.
On a standard TV, if you look really closely at the screen, you'll see little dots of color. Each dot can make red, green or blue. There are a total of 480 lines of dots. Each dot lights up with its 3 base colors, to help fill in the total picture. Since there are only 480 lines, it means you can actually see the lines and the graininess when you watch TV. It's like reading a poorly printed newspaper, where you can see lines and ridges in the photos.
Also, a standard TV has a ratio of 4:3, meaning that the screen is 4 units wide by 3 units high. It's not quite a square, it's a long rectangle. That's because when TVs were coming out, this was the radio of movie screens. Since then of course movie screens have gotten wider - but TV screens have not.
High definition fixes these problems. First, it has a MUCH better resolution. You now have a grid of 1920 x 1080 dots!! That gives you *incredibly* higher detailed pictures. You usually are very hard pressed to see the lines at all. You can see crystal clear images on this.
Next, the ratio has changed to match what we see in movie theaters - 16:9 ratio. It is much wider. This is important because your human eyeballs are meant to see the world with a wide angle. You don't look down a tunnel. When you watch a show with that wider aspect, you feel more "immersed" in the experience. Also, when you get DVDs of modern movies, you don't end up with pieces chopped off the edges. You get to see the full movie experience.
Currently, just under 20% of US homes have a HD TV set. According to studies, over half of all US households had plans to buy a HDTV in the next 12 months. You might want to be one of them, if you don't have a HD TV already!
To learn how to use the HD capabilities of your XBox, read the HDTV Cable Information