Short answers, pulled from the story.
Renaissance humanism is a worldview centered on the nature and importance of humanity that emerged from the study of classical antiquity. It first developed in Italy in the 14th century and spread across Western Europe through the 15th and 16th centuries. Its core program was to revive the literary legacy and moral philosophy of Greco-Roman civilization and use that revival to encourage virtuous civic life.
Petrarch is called the Father of Humanism because he was the first to encourage the study of pagan civilizations and the teaching of classical virtues as a means of preserving Christianity. He was also one of the great collectors of antique manuscripts, assembling a library of which many volumes did not survive.
The studia humanitatis encompassed grammar, rhetoric, history, poetry, and moral philosophy. It notably excluded logic, which had been central to medieval scholastic education. The clearest early formulation of this curriculum appeared in a letter from Tommaso Parentucelli to Cosimo de' Medici recommending books for his library collection.
Most Renaissance humanists were Christians whose goal was to purify and renew Christianity, not to discard it. They sought to return ad fontes, to the pure sources of the Gospels and the Church Fathers, bypassing medieval theological complexity. Scholars like Marsilio Ficino and Erasmus worked to show that pagan philosophy, including Platonism and Epicureanism, was compatible with their understanding of Christian teaching.
Humanism spread to Spain, France, Germany, the Low Countries, Poland-Lithuania, Hungary, and England, partly through the large-scale adoption of printing after 1500. In Spain, Francisco de Vitoria became its first great exponent and founded the School of Salamanca. In France, Guillaume Budé applied humanist methods to legal history and helped found the Collège des Lecteurs Royaux. The movement also became associated with the Reformation in northern Europe.
Hans Baron coined the term civic humanism in the 1920s to describe a strain of Renaissance thought, particularly in Florence and Venice, dedicated to republicanism and the freedom of the city-state. He argued this strand emerged around 1402 after Florence's conflicts with Visconti-led Milan. The thesis was controversial and faced sustained criticism from historians who argued the republics Baron praised were no more democratic than the monarchies he contrasted them with.