what is the difference between master degree and ms?

Don't know, are you sure you don't mean Ma or Msc as these mean master of arts or master of sciences respectively. Ms, I have never heard of and don't know what it means, could be the same as a masters degree though.

MS is the term used mostly in America for a masters (science) degree ; eqvuialent of MSc from a UK university. It's just the letters to designate it.