The Arabic language is divided into two. Modern Standard Arabic (MSA), or "fuS-Ha", on the one side. And the regional colloquial Arabic dialects on the other side.
Modern Standard Arabic
MSA is the "formal" Arabic used as the main medium of communication in writing, in the “serious” media (news, political shows, historical documentaries etc.), in educated contexts and at school. It is also the language of relgion and of the Quran.
The colloquial Arabic dialects, on the other hand, are used in everyday conversations, songs, movies and on informal occasions. Generally speaking, the dialects within a country are closer than those between different countries. So, if you speak “Syrian Arabic”, the chances are that you will understand and make yourself understood in the whole of Syria. Some country-dialects are extremely close. For example, Syrian, Lebanese, Palestinian and Jordanian Arabic form the group of Levantine Arabic or Eastern Arabic. These countries share most of the linguistic characteristics. Nevertheless, due to differences in accents or words, most speakers can spot someone from another country even within this group.
Often discussions arise as to which Arabic dialect is the closest to the classical language. Such discussions are largely futile, as all dialects have developed their own idiosyncrasies.
The most widely-used Arabic dialect is Egyptian Arabic. This is not surprising, since Egypt is the most populous Arab country. Egyptian Arabic is also widely understood, due to the importance of Egyptian cinema and literature, as well as music and other forms of entertainment throughout the region.
Most Arabs can easily understand the dialects of different regions, not least thanks to pan-regional television channels and programs. However, many Arabs state that they cannot understand the Moroccan dialect. This is likely due to the fact that Moroccan Arabic contains a large number of loan words and expressions from the French language, thereby making comprehension difficult.
What to learn?
Our recommendation to Arabic learners is that they learn both MSA and a regional Arabic dialect. Ideally, this would be followed by another regional dialect, to ensure maximum coverage of the Middle East. It is also true, that learning Arabic dialects gets easier once you have a firm grasp of two dialects. You will start to see the similarities and commonalities of Arabic dialects. Often simplifications of the classical language are reflected in many dialects in the same way.