This mark - " - is used similarly to this mark - . - in English; for acronyms. For instance, U.S.A. - United States of America.
ארה''ב - ארצות הברית
The difference is that with Hebrew acronyms they don't use the first letter of every word, like U.S.A.. Rather they use parts of each word. So the Hebrew acronym above used the first two letters of 'aretzot' and the first two of 'habrit'. I'm not sure why the put the - " - symbol where it is but I'm sure the people that make up rules for Hebrew know why.
Note: Aretzot Habrit is not a good translation for United States of America, in my opinion. I think a better translation would be
המדינות המיוחדות של אמריקה
It's an awesome translation IMHO.
Does chutz la'aretz mean abroad? I was under the impression it only means abroad if your frame of reference is Israel specifically. Someonein New York who travels to France is going abroad but he would not say that he will travel to Chutz La'aretz. Unless I am mistaken this term means "outside of Israel"