HDMI cable?

It's a single cable that can carry high definition video and audio from console to TV.

This compares to AV cables that has 3 ports, and can support only up up 480i and component cables that have 5 ports, but can also do HD.

HDMI's carry digital signals vs. AV and component that are analog.

Most newer TVs today are going digital only, so is the only way to connect external devices to your TV.

I'm not overly acknowledged on this nor video games, because I don't really play them much nor can't lol. So I see they have acquired better answers and actually know this so congrats guys and continue to input in others! :)

Improves the audio & video quality. The graphics wouldn't be any better, just display better.