Hi Gloria
I know we talked about this through PMs but just thought I'd share some of it here if anyone else stumbles upon this thread and is interested...
Basically, with Arabic, you have the classic Arabic which is the written Arabic. It is also used in speech in formal occasions since it is understood by all Arabs.
Then, you have different spoken dialects and slang words, mainly differing by country but also you'll find some variations of these dialects within the countries themselves.
Usually most Arabs understand each other, though some dialects might take some getting used to. But the dialects are not totally different so its usually easy to communicate.
The most widely understood dialects are the Egyptian & Lebanese dialects because they are prevalent in the media. The least understood dialects are Algerian, Tunisian and Moroccan dialects.
I don't know which dialect Rosetta stone teaches BUT I think she must teach the classic arabic since it's the "proper" arabic...