So if you in a small room, you can make smaller motions, if your in a larger room, you can make larger motions and it will register the same.
http://news.cnet.com/8301-17938_105-20001100-1.html
And for all of you that said this is the same as eyetoy, your wrong.
Eyetoy doesn't have this feature
Eyetoy doesn't have two cameras like Natal
Eyetoy doesn't have voice recognition
Eyetoy can't recognize figer motions
Eyetoy cant see in image and put it on screen (Ex. the skateboard)
Man Natal is amazing! Can't wait to use it!
http://www.xbox.com/en-GB/news-features/news/Project-Natal-in-detail-050609.htm