what is ogg?

i've had soo many people tell me that ogg is better than mp3, how? i know ogg is opensource, but as long as the bit rate's the same does it really matter in terms of quality? or does the differnce matter in size ?

As long as it doesn't play out ot the box on iTunes/OS X and my iPod, ogg isn't relevant to my life as far as I am concerned.