Arabic usually refers to Modern Standard Arabic, the language of present-day media across the middle east. This is a slightly simplified and modernized version of Classical Arabic, the language of the Quran. "Arabic" can also refer to one of the many national or regional dialects spoken daily across the Middle East, which can sometimes differ enough to be mutually incomprehensible, but are usually similar enough for natives to understand.
Arabic is a Semitic language, closely related to the Hebrew language. Many dialects are spoken in modern Arabic states such as Egypt, Lebanon, and Morocco, but all of these countries use Modern Standard Arabic for printed media. Its function however is different from Western standard languages: it is mainly the language of the Quran (in its Classical form), and is not spoken in everyday life. Consequently, prestigious vernacular varieties have some of the functions that standard languages have in Western countries (see Chambers, Sociolinguistic Theory). Arabic is the language of Islam, but is also spoken by Arab Christians and Oriental Jews.
Voiceless plosives: /t/, /t'/, /k/, /q/, /?/
Voiced plosives: /b/, /d/, /d'/, /dZ/ (/dZ/ is /g/ for some speakers, i.e. a plosive)
Nasals: /m/, /n/
Laterals: /l/ ([l'] only in /?alla:h/, the name of God, i.e. Allah)
Semi-vowels: /w/, /j/
/'/ is used to indicate velarization and pharyngalization (=emphatic consonants; usually transcribed as dotted consonants). The other symbols are SAMPA.
Vowels and dipthongs can be (phonologically) short or long.