Pope Leo XIV calls for end to wars in Ukraine, Gaza

Of all the ceremonies associated with electing a new pope, the one most familiar to the general public is the smoke that emanates from a stovepipe chimney atop the Sistine Chapel after every round of balloting.

Black smoke -- fumata nera in Italian -- indicates an inconclusive vote, while white smoke -- fumata bianca -- will signify that a new pope has been elected. Along with the white smoke, the bells of St. Peter's Basilica will ring to proclaim the event to the world.

The ceremonial smoke is not created by the burning of the ballots. The voting slips are burned in a stove that dates back to the 1922 conclave and is set up for the occasion in the Sistine Chapel.

The smoke that wafts from the stovepipe chimney is created using chemical pellets that are burned in another stove that's connected to the chimney, which is temporarily erected atop the Sistine Chapel just for that purpose.

Assuming the elected cardinal accepts the office, the new pope's identity is typically revealed within an hour of the final ballot, after he chooses the name by which he will be known as pope.

The new pope then emerges onto the balcony to present himself to the world and deliver his first blessing to the crowd gathered below in St. Peter's Square.

-ABC News' Christopher Watson

As Vatican City begins to fill with the faithful on Wednesday morning, the weather forecast calls for temperatures in the mid-60 degrees Fahrenheit, with midday showers expected, according to the Italian Meteorological Service.

More than 25,000 people are expected to gather into St. Peter's Square on Wednesday, along with crowds of people spilling over into the nearby roads.

About 4,000 security personnel are on hand, along with about 1,000 volunteers. And about 5,300 journalists from around the world will be present, waiting for news from the conclave.

-ABC News' Joe Simonetti

Each member of the 133-cardinal conclave will write his choice on a paper ballot slip, fold it once in half and carry it held aloft between two fingers to the Sistine Chapel altar, where he will deposit it in a special urn placed there. In order to make the balloting secret, conclave members are instructed to write their votes "as far as possible in handwriting that cannot be identified as his."

Any conclave member who cannot attend in person due to illness or infirmity will cast their ballot from their room in the Domus Marthae Sanctae, where they're collected, placed in a lockbox and carried to the Sistine Chapel.

The votes are then counted by three scrutineers who affirm what is written on each ballot and then announce it to the conclave, so the cardinals can record the votes themselves. If the number of ballots cast is different than the number of cardinal electors, those ballots are discarded and burned and a new vote taken.

The candidate who secures two-thirds of the votes is elected pope.

Up to four rounds of voting can typically take place in a day. If no clear choice has emerged after three days, balloting is suspended for 24 hours to allow cardinal electors time to reflect. Another seven rounds of balloting then takes place, followed by another break, and so on.

If no pope is elected after 33 or 34 votes -- generally about 13 days -- then a new rule introduced by Pope Benedict XVI decrees that the two leading candidates as determined by previous ballots will engage in a runoff vote.

The candidates themselves, if they're members of the conclave, cannot vote in the runoff but are present for it. Whichever candidate receives the necessary two-thirds majority of the votes is the new pope.

-ABC News' Christopher Watson

Hundreds of Catholic cardinals -- of whom 133 will be voting -- have gathered at the Vatican to begin the process of electing the next pope on Wednesday.

The cardinals will first attend a mass at St. Peter's Basilica at 10 a.m. local time (4 a.m. ET).

The 133 voting cardinals will then enter the Pauline Chapel at around 4:15 p.m., from which they will proceed to the Sistine Chapel to take their oaths at approximately 4:30 p.m.

The master of ceremony will then oversee the official start of the conclave at approximately 5 p.m.

-ABC News' Phoebe Natanson and Joe Simonetti