Why the Footwashing Ceremony at Passover?

Baptized Members of the Church of God partake each year at Passover evening of the symbols of bread and wine, but they also participate in the footwashing ceremony. Why did Christ introduce the footwashing ceremony, and what does it mean for us today? How do we understand Christ’s statements in response to Peter’s initial refusal to accept Christ’s washing of his feet? And is there a relationship between the correct baptism, which only occurs once in a lifetime of a converted person, and the footwashing ceremony which is being observed annually?