As a whole, Arabic is considered a Neo-Aramaic language. Ironically (given geo-political circumstances), one of its close relatives is Hebrew. Worldwide, over half a billion people speak Arabic as a first or second language.
Modern Standard Arabic (foosha), spoken in most Gulf and Middle Eastern nations, developed from Classical Arabic, which dates to inscriptions from the 4th century. Classical Arabic is also the language of Islam’s Qu’ran. People sometimes use terms like “Literary Arabic” or “Standard Arabic” to refer to one or the other interchangeably. The most important thing to note is that Modern Standard Arabic is the language of Arab media and literature, while Classical Arabic is the language of Islamic texts.
The Arabic alphabet consists of 29 characters. Unlike English, Arabic letters have a one-to-one correspondence to sounds. For example, while in English the sounds at the beginning of the words “there” and “three” are represented by “th” in both cases, Arabic has distinct characters for both sounds.
Many Arabic words contain glottal stops, and some Arabic vowel sounds (particularly ayn) require the use of throat muscles that Westerners do not usually exercise when speaking.
Egyptian Arabic is the most widely recognized of all the Arabic dialects, as it has been exported throughout the Arab world in music, movies and other areas of popular culture. A speaker of Egyptian Arabic, therefore, can sometimes make himself understood in another Arab without speaking Modern Standard Arabic, while the opposite might not necessarily be true.
Egyptians often refer to their dialect as Arabic slang, and at times it bears little resemblance to Modern Standard Arabic. In other cases, the two are extremely similar. The Modern Standard Arabic word for pen, for example, is qalam, but an Egyptian will remove the “q” sound and say alam. Along the same lines: in Egyptian Arabic, the consonant corresponding to the English “g” is pronounced like the g in “good,” while in Modern Standard Arabic is usually closer to a soft “j.”
Someone who speaks Egyptian Arabic will undoubtedly have an easier time learning Modern Standard Arabic than does not (especially since the alphabet remains the same), and vice versa, though it will still require a great deal of time and effort.