Short answers, pulled from the story.
Arabic is spoken by as many as 380 million native and non-native speakers in the Arab world. This makes it the fifth-most spoken language in the world and the fourth-most used language on the Internet by users.
Western linguists divide Standard Arabic into Classical Arabic, the language of the Quran, and Modern Standard Arabic, which largely follows Classical grammar but drops some constructions and adds new vocabulary for the industrial era. Arabic speakers themselves generally do not distinguish the two, calling both al-fuṣḥā, the eloquent Arabic.
The Arabic alphabet descends from Aramaic through the Nabatean script. From the 4th to 6th centuries the Nabataean script evolved into the Arabic script of the early Islamic era, and the oldest surviving Arabic papyrus from 643 CE already uses dots to give the full 28-letter alphabet.
Abu al-Aswad al-Du'ali, who lived from roughly 603 to 689, is credited with standardizing Arabic grammar, called an-naḥw, and pioneering a system of diacritics. Al-Khalil ibn Ahmad al-Farahidi, who lived from 718 to 786, compiled the first Arabic dictionary, Kitāb al-'Ayn, and the first comprehensive description of Arabic was Sībawayhi's al-Kitāb.
English words borrowed from Arabic include admiral, adobe, alchemy, alcohol, algebra, algorithm, almanac, amber, assassin, candy, carat, cipher, coffee, cotton, hazard, magazine, mattress, sofa, tariff, and zenith. Most reached English indirectly through other Mediterranean languages.
Arabic uses a nonconcatenative root-and-pattern morphology, where a root of usually three bare consonants is fitted into a discontinuous pattern to form words. From the single root k-t-b for "write" come katabtu "I wrote," kitābun "book," kātibun "writer," and maktabun "desk, office."
Arabic exists in a diglossic situation where a single written standard unites many spoken varieties that can differ enough to be mutually unintelligible. Moroccan Arabic is hardly comprehensible to Arabic speakers east of Libya, and linguists often compare the spread of Arabic dialects to the Romance languages over roughly 1500 years of divergence.