What is the Pidyon HaBen ceremony?

G-d told the Jewish people that their first-born sons must be dedicated to G-dly service. When the Jews sinned with the Golden Calf, G-d commanded that the Levites, who had not sinned, serve instead of the first-born sons. The details of the redemption of the first-born (pidyon haben) is in Num. 18: 15-16. The first-born son of the mother is redeemed on the 31st day after birth. At the Pidyon Haben ceremony, the father gives a Kohain five silver coins in lieu of his son. The son of a kohain or levi, or the son of the daughter of a kohain or levi is not redeemed. A festive meal follows the ceremony. If one was not redeemed as a baby, a man is responsible, after the age of bar mitzva, to redeem himself.