Zoroastrianism is the religion and philosophy based on the teachings ascribed by the prophet Zoroaster (Zarathustra, Zartosht). Mazdaism is the religion that acknowledges the divine authority of Ahura Mazda, proclaimed by Zoroaster.
As demonstrated by Zoroastrian creed and articles of faith, the two terms are effectively synonymous. In a declaration of the creed — the Fravarānē — the adherent states: "…I profess myself a devotee of Mazda, a follower of Zarathustra." (Yasna 12.2, 12.8)
While Zoroastrianism was once the dominant religion of much of Iran, the number of adherents has dwindled to not more than 200,000 Zoroastrians worldwide, with concentrations in India and Iran.
The Zoroastrian faith is described by its adherents as Mazdayasna, the worship of Mazda. In the Avesta, "Ahura Mazda is the highest object of worship", the first and most frequently invoked divinity in the Yasna liturgy. In Zoroastrian cosmogony and tradition, all the lesser divinities are also creations of Mazda. (e.g. Bundahishn III)
Information about the life of Zoroaster derives primarily from the Avesta, that is, from Zoroastrian scripture of which the Gathas - the texts attributed to Zoroaster himself - are a part. These are complemented by legends from the traditional Zoroastrian texts of the ninth to twelfth century.
The Gathas contain allusions to personal events, such as Zoroaster’s triumph over obstacles imposed by competing priests and the ruling class. They also indicate he had difficulty spreading his teachings, and was even treated with ill-will in his mother’s hometown. They also describe familial events such as the marriage of his daughter, at which Zoroaster presided.