From Academic Kids
In animals, vocalization is a means of communication generated in many cases by their primitive versions of vocal chords.
In birds, it may be achieved by whistling but can communicate a number of things including danger.
In humans, it is a special means of communication called speech.
In languages with consonantal alphabets (sometimes inaccurately termed abjads), vocalization refers to the process of adding vowel markers (Arabic tashkil, Hebrew niqqud). See also: Arabic alphabet, Tiberian vocalization, Syriac alphabet.