Question about qnames vs curies

Hi!
I am a student from Brazil and i have a question about namespaces for my
thesis:

How is the real and pratical difference of Qname and CURIE ?
I read this:
http://www.xml.com/pub/a/2007/04/04/introducing-rdfa-part-two.html?page=1
And i conclude that only advantage is allow numeric names, like
"[ime:2224445]"

Thanks!!!
Celso