Cracking jokes and ad-libbing, the new pontiff addresses the world's media and explains why he chose to name himself after St Francis of Assisi. Lizzy Davies reports from Vatican City

As he walked on to the stage of the Vatican's vast Paul VI audience hall on Saturday, Pope Francis was still wearing the white cassock, plain crucifix and black shoes that have characterised his fledgling papacy's pared-down aesthetic.

In his first encounter with the thousands of weary journalists who have been covering the Vatican in recent action-packed weeks, the first Latin American and Jesuit pontiff endeared himself to them by expressing gratitude for their labours. "You've been working, eh?", he chuckled, in the informal style that is fast becoming his trademark.

But some of the loudest applause from the audience was reserved for when the man of simple habits explained why he had chosen to name himself after St Francis of Assisi, the saint who devoted his life to peace and the poor.

In conclave, the Argentinian said, when the votes were being counted and things seemed to be becoming – in his own words "a bit dangerous" – the cardinal sitting next to him, an old friend from Brazil, embraced him and said: "Don't forget the poor."

In a clear signal of his desire to reset the priorities of the embattled Catholic church after Benedict XVI's intellectual, remote-seeming reign, Francis added that the reminder had made him think of St Francis – a man "who wanted a poor church". "Ah, how I would like a church," he said, "that is poor and is for the poor."

Juan Camilo, a 23-year-old Colombian in the audience, was impressed. "I liked most of all this part, because it is a sign of transformation of the change towards the poor," he said. "And surely it will be a sign of an improvement of the relationship between the church and its hierarchy and the people. Because [in recent years] the church hasn't been so open to the people."

Looking relaxed and settled in his new role, Francis, 76 – who delivered his inaugural homily off the cuff and veered from his notes during an address to cardinals on Friday – once again proved his penchant for improvisation as he cracked jokes and recounted the anecdote in the Sistine chapel.

While he had decided on the name Francis, he explained with a grin, other cardinals had their own suggestions, including Clement XV as a way of getting back at Clement XIV, who had suppressed the Jesuits. And, in an allusion to the desire for reform with which many cardinals entered conclave after years of scandals and controversies, he said that another had proposed that Jorge Bergoglio name himself after Adrian VI, the 218th pontiff who sought to reform the church and crack down on abuses of power and corruption in the hierarchy.

The meeting with the media – 5,600 of whom had been accredited to cover the transition between Benedict's resignation and Francis's election – had been applauded when first announced by spokesman Federico Lombardi. In the end, as with Benedict's own parallel audience in April 2005, the interaction between pontiff and press was strictly one way. "It is not a press conference," the Vatican clarified.

In a brief but warm message to journalists, Francis chose not to repeat a colourfully worded claim made last year in which he accused them of focusing on and exaggerating the negative sides of the Vatican. He did, however, urge them to "always try to better understand the true nature of the church and even its journey in the world, with its virtues and with its sins".

Afterwards a string of journalists and communications helpers lined up to be greeted personally by the pope – some of the men embracing him in bear hugs. The reporters included Giovanna Chirri, the Latin-speaking Vatican specialist for the Ansa news agency who broke news of Benedict's resignation, and a visually impaired radio journalist whose guide dog also received a papal blessing – a fitting image for a pope seeking inspiration from the patron saint of animals.

The coming days are looking busy for Francis. Today he will deliver his first angelus, or Sunday prayer. Tomorrow he will meet the Argentinian president, Cristina Fernández de Kirchner, whom he has taken to task for her pioneering moves to make the pope's home country the first in Latin America to legalise gay marriage.

In an inauguration mass celebrated by dignitaries from all over the world, Francis will be officially made pope on Tuesday. Leading the Anglican delegation will be the archbishop of York, John Sentamu. Archbishop of Canterbury Justin Welby, whose predecessor, Rowan Williams, attended Benedict's installation in 2005, is unable to attend as he is on a prayer pilgrimage in preparation for his own enthronement on Thursday. The Queen will be represented by the Duke of Gloucester.

Of all his future engagements, however, the one that particularly stands out is his historic meeting, planned for Saturday, with his predecessor at his temporary retirement home in Castel Gandolfo. The Vatican said yesterday that the two popes – current and emeritus – would meet privately.

The virtually unprecedented dynamic has prompted speculation over the kind of role – if any – Benedict will play in church affairs. The first pope to resign for nearly 600 years has, however, insisted he will be "hidden from the world". Francis has appeared comfortable with the unusual situation, paying an emotional tribute to his predecessor from the balcony of St Peter's basilica in his first public appearance as pope.