King David assigned each of the 24 priestly clans to a weekly watch (Heb.
“mishmeret” = משמרת) during which its members were responsible for maintaining the schedule of offerings at the Temple in Jerusalem, in accordance with 1Chronicles 24:3–5.
The second is Potiphera, priest of Heliopolis, then Jethro, priest of Midian both pagan priests of their era.
Moses was supposed to receive the priesthood along with the leadership of the Jewish people, but when he argued with God that he should not be the leader, God then chose Aaron as the recipient of the priesthood.
During the existence of the Temple in Jerusalem, kohanim performed the daily and holiday (Yom Tov) duties of sacrificial offerings.
The term is used colloquially in Orthodox Judaism in reference to modern day descendants of Aharon.
In the Samaritan community, the kohanim have remained the primary religious leaders.
Today, kohanim retain a lesser though distinct status within Rabbinic and Karaite Judaism, and are bound by additional restrictions according to Orthodox Judaism.