Francis’ successor will be selected by cardinals at the conclave that begins 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.

As the conclave to elect the next pope begins Wednesday at the Vatican, four candidates have emerged as clear favorites—Cardinals Pietro Parolin, Luis Antonio Tagle, Matteo Zuppi and Pierbattista Pizzaballa.