There is a saying in Arabic: "Every language is like the sea but the Arabic language is like the ocean."
This refers to the richness of Arabic, whose vocabulary is among the largest of any language on earth.
There are other challenging factors for those who wish to master the Arabic tongue, and the difference between spoken Arabic and literary Arabic is primary among them. The Arabic you hear in the street bears little resemblance to literary Arabic. Literary Arabic is not only the language of the Koran, but it is also found in every kind of book, in newspapers, and in official documents. Arabic heard on the radio is also literary Arabic.
Everyday spoken Arabic is vastly different from literary Arabic. To make matters still more complicated, Arabic dialects vary considerably from place to place and even over short distances. For instance, in Israel today, the Arabic spoken in cities differs from the Arabic spoken in villages, which is still different from the Arabic spoken by the Bedouins.