Francis’ successor will be selected by cardinals at the conclave that began on May 7. Cardinals, known as the “princes of the church,” rank just below the pope in the Roman Catholic Church; together, they are known as the College of Cardinals. When a pope dies, the college chooses a successor.

A conclave will go on for as long as needed. The longest was almost three years from 1268 to 1271. Some have been a day. The conclave that selected Pope John Paul in 1978 lasted less than three days. The conclave that chose Pope Francis took about two days.