(John the Baptist Baptizing Jesus, by Harry Anderson)
The Aaronic Priesthood (also known as the Levitical Priesthood or Priesthood of Aaron) is the lesser Priesthood modeled after the older brother of Moses, Aaron the Levite. The Aaronic Priesthood was carried by Aaron during the Exodus to help support his older Brother’s Melchizedek Priesthood. Aaron was a great leader of the Hebrews during the Exodus and Moses could not have properly exercised his Priesthood authority without the help of Aaron.
John the Baptist also had the Aaronic Priesthood conferred upon him, allowing him to Baptize and prepare for the coming of the lord Jesus Christ.
As the Prophet Joseph Smith translated the Book of Mormon, he found mention of baptism for the remission of sins. On May 15, 1829, he and his scribe Oliver Cowdery went into the woods to inquire of the Lord concerning baptism. As they prayed, “a messenger from heaven descended in a cloud of light.” This messenger was John the Baptist, the prophet who had baptized Jesus Christ centuries earlier. John the Baptist, now a resurrected being, laid his hands on Joseph and on Oliver and conferred upon each of them the Aaronic Priesthood, which had been taken from the earth during the Great Apostasy. With this authority, Joseph and Oliver were able to baptize one another. (See Joseph Smith-History 1:68-72.)