Tajwid rules cover several interlocking dimensions of Quranic recitation, beginning with makharij al huruf, the precise physical point in the mouth or throat where each Arabic letter must be articulated, a level of phonetic precision considerably more exacting than ordinary conversational Arabic pronunciation requires.
Beyond individual letters, tajwid governs how adjacent sounds interact, rules determining when a letter is fully pronounced, softened, merged into a following sound or nasalized depending on its neighbors, and it specifies precise durations for elongated vowels, madd, that can otherwise be easily shortened or lengthened incorrectly by an untrained reciter. Two broad recitation styles sit atop these technical rules: murattal, a measured, relatively unornamented style used for private recitation, study and much broadcast recitation, and mujawwad, a slower, more melodically elaborate style associated with public performance and competition, in which a skilled qari draws on considerable vocal artistry while still remaining bound by the same underlying tajwid rules. Because these rules are held to preserve the precise sound of the Quran as revealed and transmitted, tajwid is taught as inseparable from the text itself rather than as a separate performance skill layered on top of it, and formal instruction typically begins early in a student's Quranic education, well before more advanced study of interpretation or law.