Cardinals form the Pope's most senior body of counselors and, collectively as the College of Cardinals, the constitutional mechanism by which the Roman Catholic Church elects a new pope. The rank is not a sacramental order; a cardinal's underlying priestly or episcopal ordination is unaffected by elevation to the cardinalate, and a small number of appointees in history, though not in modern practice, received the honor without prior episcopal consecration. Historically, cardinals were divided into three ranks, cardinal bishops, cardinal priests and cardinal deacons, reflecting the office's origin in the senior clergy attached to Rome's own suburbicarian dioceses and the city's principal churches, the titular churches, or tituli, still symbolically assigned to each cardinal today.
Modern cardinals typically head major archdioceses, senior Vatican offices, dicasteries, within the Roman Curia, or hold emeritus status after such service, giving the College a working structure that spans the Church's central government and its largest local churches simultaneously. Paul VI's 1970 decree limiting conclave voting rights to cardinals under eighty formalized a distinction between active elector cardinals and older cardinals who retain the honor and most advisory functions but cannot vote for a new pope, a change intended to keep the electing body from growing indefinitely as life expectancy increased.