Arabic, according to the latest statistics, is the 5th most spoken language in the world. There are 60 countries where the language is spoken, with a total of 242 million people speaking Arabic as their first language. The primary country where it is spoken is in Saudi Arabia and it is the official language in more than 20 countries, as well as in the Arab League, the United Nations, the African Union and the Organization of Islamic Conference.
As a language group, Egyptian Arabic has the most number of speakers at 55 million, followed by Algerian Arabic with 26.7 million. Arabic, which belongs to the Afro Asiatic family, has a history that stretches as far back as the 6th century. It belongs to the Central Semitic language branch and closely akin to Phoenician, Ugaritic, Hebrew and Aramaic.
As a religious language, it is spoken by more than one billion Muslims around the world and is learned (in different proficiency levels) as a revered liturgical language by Muslims located in Africa, China, Malaysia and Pakistan.
The term Modern Standard Arabic is sometimes used in the West to refer to the language of the media as opposed to the language of "classical" Arabic literature; Arabs make no such distinction, and regard the two as identical. The word "Arabic" also refers to the many national or regional dialects/languages derived from Classical Arabic, spoken daily across North Africa and the Middle East, which sometimes differ enough to be mutually incomprehensible. These dialects are not frequently written, although a certain amount of literature (particularly plays and poetry) exists in many of them, notably Lebanon and Egypt.
When traveling to any Arabic-speaking country, it is important to remember that a different Arabic dialect is used in each region, which other people may or may not understand. It is important to note that educated speakers of the language have a tendency to mix Standard Arabic with their dialects in varying degrees. For clarity, there are about four principal regional dialects today that's spoken in the Arab world (with various dialectic variations):
Maghreb Arabic (Spoken in Tunisia, Algeria and Morocco)
Egyptian Arabic (Spoken in Egypt and it is the most understandable dialect among almost all Arabic Speakers)
Sudanese Arabic (Spoken in Sudan)
Gulf Arabic (Spoken in the Gulf Region; including Kuwait, Iraq, Saudi Arabia, Bahrain, Qatar, UAE and Oman.
Levantine dialect (Lahjah Shamiyah) group is spoken for everyday communication in Palestine, Jordan, Syria and Lebanon and is part of the Mashriqi (Eastern Arabic) Arabic that also includes Peninsular Arabic and Mesopotamian Arabic. The Levantine dialect is a widespread dialect that is used in the 100- to 200-km wide coastal regions along the Eastern Mediterranean.
Mesopotamian Arabic is a group of Arabic dialects that are mutually intelligible to each other. It is spoken in the Iraq basin and in southeastern Turkey, Iran and Syria. Iraqi communities in other areas also speak Mesopotamian Arabic.
There are still a lot of Arabic dialects varying in different countries and even provinces inside the same country, but the above are the most common.