When a reigning pope dies, an immediate duty falls to the camerlengo, a cardinal whose title translates to "chamberlain." The camerlengo declares the pope is deceased and administers the Holy See until a successor is chosen. The current camerlengo is Cardinal Kevin Farrell, the first American in that post.
Funeral rites for the late pope are held for nine days as he is mourned and celebrated. Conclaves must begin within 15 to 20 days after a pope dies or resigns.
Upon the pope's death, the dean of the College of Cardinals calls the cardinal electors to the Vatican. There are currently 138 of them. To join the conclave, cardinals must be under 80 years old.
During the conclave, the cardinals live in the Domus Sanctae Marthae, a hotel-like facility next to St. Peter's Basilica. It's where Pope Francis opted to live, rather than in the Apostolic Palace's papal apartments. The residence has been compared to a three-star hotel.
The rituals take place according to rules popes have refined over the centuries, clarifying the timeframe and obligations. But the conclave itself must be obscured by "total secrecy," as Pope John Paul II wrote. Cardinal electors must sign an oath of secrecy and seclusion, under threat of excommunication.
The process involves multiple rounds of voting over several days. All the conclaves from the 1900s onwards have lasted less than four days. Francis was elected pope on the conclave's second day, for instance.
After a successful vote, the winning candidate is asked two questions: whether they accept their election, and what name they choose.
Then official documents are signed, the pope is fitted with new attire and the decision is announced. The senior cardinal deacon will appear on the balcony over St. Peter's Square, announcing, Habemus Papam! — "We have a pope!"