With more than 1 billion practicing Catholics in the world, Pope Benedict XVI's first visit to the U.S. will be a major event viewed around the world.

Yet many are left wondering exactly who the pope is, what he does and how much power he truly holds.

In the Catholic religion, the pope is recognized as the "Vicar of Christ" -- the primary contact between heaven and earth. His judgment is infallible and his word is final. He is elected to this authoritative position by his fellow clergymen in what is called a papal election.

Aside from governing the Catholic Church, the pope must also do his best to spread its message. He travels around the world and speaks his faith. The pope also leads a weekly Sunday service in Vatican City, Rome.

This spiritual message, with its massive following, remains the source of the pope's power. Regardless of the Catholic laws that declared his religious sovereignty, the pope's role has shifted dramatically throughout history toward one of relative humility.

Whereas the popes of past centuries crowned emperors, openly practiced nepotistic piousness (such as the "papal dynasty" of Pope Callixtus III) and even proclaimed ethnic secularism (often against typically non-Catholic ethnicities), today's pope focuses on spiritual resolutions to life's tribulations.

Benedict, in his modern adaptation of the Catholic doctrine, recently updated the list of sins to include polluting the Earth and genetic manipulation, such as embryonic stem-cell research.

In recent years, under Benedict and his predecessor John Paul II, the church has held scientific conferences on global warming and has taken steps to make the Vatican more "green."

It is no doubt that many of these modern sins will be on Benedict's mind when he sees Bush on April 16. Benedict has publicly criticized the plight of consumerism on numerous occasions -- something that has significantly contributed the U.S.'s debt crisis -- and continues to denounce the ongoing wars in Iraq and Afghanistan.