Zoroastrian priesthood, unlike many single-tier clerical systems, is organized as a sequence of ordinations that mark increasing ritual competence rather than as one undifferentiated priestly status. A candidate, traditionally born into a priestly family though contemporary practice varies by community, first undergoes the navar ordination, which qualifies him to perform the outer liturgical ceremonies generally associated with the herbad rank; a further martab ordination is required before a priest may perform the inner, more restricted ceremonies, principally the high liturgies conducted within the inner sanctum of a fire temple, that mark the mobed rank properly. A priest who has completed navar but not martab functions and is generally described as a herbad, competent in a real and formally recognized sense but not yet qualified for the tradition's highest liturgical work.
The rank also carries an older, broader sense as teacher: the Avestan term aethrapati, ancestor of herbad, denotes specifically a religious instructor responsible for training others in correct ritual recitation and doctrine, and Zoroastrian tradition has generally treated priestly competence and pedagogical competence as closely linked rather than as separate skills, since correct oral transmission of liturgical Avestan, historically preserved with very little reliance on written text in daily practice, depended on trained teachers passing exact recitation down directly rather than on manuscripts alone.