The world won’t know the next leader of the world’s Catholics until he appears before a throng of supporters in St. Peter’s Square. But in the coming days, powerful members of the Catholic Church from around the world will take part in a process that is part spiritual and part pragmatic.

Here's everything you need to know about a conclave, the secret, centuries-old process used to select a new pope.

Pope Francis chose 149 of the current members of the college, most of whom will help choose his successor as cardinal electors. Though cardinals over the age of 80 cannot vote in the conclave, they do participate in pre-conclave meetings, called general congregations, and can still have an influence over who is chosen.

Leading the 1.4 billion-strong Catholic Church. Location: Vatican City. There are no official candidates for the papacy, but some cardinals are considered “papabile,” or possessing the characteristics necessary to become pope.

Representing a little over 4% of the globe’s Catholics but nearly 8% of those who will participate in the papal conclave, the 10 American cardinals in Rome this week already have outsized numerical influence in choosing the next pope.