Pope Benedict XVI waves in St. Peter's Square in the Vatican in December 2012. Benedict, 85, announced on Monday, February 11, that he will resign at the end of February "because of advanced age." The last pope to resign was Gregory XII in 1415.

Why has Pope Benedict XVI resigned?(CNN) -- In an unexpected move, Pope Benedict XVI -- born Joseph Ratzinger -- has announced that he is to resign. Benedict was elected pope in 2005 after the death of Pope John Paul II. We explore what the surprise announcement means for the Catholic Church.

In his statement, Pope Benedict -- who turns 86 in April -- said he had come to the certainty "that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry."

Vatican spokesman the Rev. Federico Lombardi said Pope Benedict had the right and potentially the duty to resign.

But he stressed that the pope's decision was not because of any external pressured.

When will the next pope be elected?

A meeting of the College of Cardinals to elect the next pope will be held. The gathering is known as a "conclave."

Vatican spokesman Federico Lombardi said there would be elections some time in March and he anticipated that there would be a new pope before Easter.

Lombardi said Vatican scholars were studying the constitution to determine exactly when the conclave would begin.

What will Pope Benedict do after his resignation?

Lombardi said it was expected that Pope Benedict would devote his time to reflection and prayer.

In his statement, Benedict said he wished "to also devotedly serve the Holy Church of God in the future through a life dedicated to prayer."

Lombardi said he didn't expect the pope to be given any other duty, given his age, and he said Benedict would no longer be involved in decision making or administrative duties.

Pope Benedict was "very discreet" and was "not someone who will interfere" or create issues in terms of his successor, he said.

Where will the former pope live?

After he steps down, Benedict will move to the pope's summer residence, Castel Gandolfo.

At a later date he will move into in a monastery at the Vatican.

The monastery has recently been renovated and extended to include a small chapel.

What will Pope Benedict be known as once he has stepped down as pope?

According to the Catholic Bishops' Conference of England and Wales, Pope Benedict will return to being known as Cardinal Joseph Ratzinger. It said he would be addressed as his eminence or Cardinal Ratzinger.

However, Lombardi later told reporters it was hard to imagine that the pope would be called a cardinal.