An archbishop is usually the bishop of a major metropolitan archdiocese. A cardinal is a member of the college of cardinals, and, according to current requirements, is usually at least a bishop; however, the regulation that a cardinal not already ordained to the episcopate be so ordained can be dispensed, as it was with Avery Cardinal Dulles, S.J., for example. So, with permission, it is possible for a layman or a priest to be a cardinal.
