What is the difference between an ao dai and an xuong xam dress

I've seen people wearing both of these dresses and I am wondering what is the difference between them.

"Ao Dai" is traditional dress of Viet Nam. Xuong Xam dress (in Chinese) you can wear without pants, but "Ao Dai" need to be wearing with pants.  :D

You have Vietnamese nickname, and you don't know the difference?
Here the link: quangcao24gio.net/chi-tiet/xem/14/30184-ao-dai-ba-ba-suon-xam

This is "sườn xám"
http://img02.taobaocdn.com/bao/uploaded/i2/T1UBe2XlRcXXbys6o0_035700.jpg