In the present day, hērbad is the lowest rank in the Zoroastrian priesthood, and is granted following the basic navar ceremony that marks the beginning of theological training.
Middle Persian 𐭧𐭩𐭫𐭯𐭲 harpat (Pahlavi ʼyhlpt) derives from Avestan 𐬀𐬈𐬚𐬭𐬀𐬞𐬀𐬌𐬙𐬌 aeθrapaiti, which the Avesta uses denote a priestly teacher whose students (aethrii) would be taught to recite the sacred texts.
There is some evidence that suggest that already by the 6th century, hērbads performed advanced theological tasks, including translations and interpretation of Avestan texts.
For Zoroastrian laypersons, the distinction between the two groups was at best theoretical and by the 10th century, the term hērbad had lost most associations of scholarship and eventually came to refer to priests that had no theological authority.
In the 16th century, the Rivayat epistles encouraged the Indian Zoroastrians to distinguish between priests capable of officiating at a Vendidad reading and the others.