WHO: The Reformation had three main actors: Martin Luther, John Calvin, and King Henry VIII of England. Luther was a monk in Germany who wrote a text called 95 Theses, which protested certain practices of the pope and Catholic church. Calvin was a French Protestant who was invited to live safely in Switzerland and practice his own Reformed doctrine. King Henry VIII was the monarch of England who began England's path towards its own religion, which was something of a compromise between Catholicism and Calvinism.
WHAT: Luther's 95 Theses led to a peasant uprising in Germany, although Luther himself sided with the royal family of Germany. Calvin's practice was called the Institutes of the Christian Religion. Henry declared that the king would have final authority in the English church, dissolved all of England's monasteries, and created versions of the Bible written in English, not Latin.
WHEN: Luther posted his theses in 1517, and in 1521 he was excommunicated from the Church. About 30 years later, in 1555, the Peace of Augsburg brought about the coexistence of Catholics and Lutherans in Germany. Calvin began his Geneva practice in 1541, and for the next 400 years, Calvinisim remained a powerful player in religion and economics. Henry detached England from the church in 1534.
WHERE: All across Europe, but primarily Germany, Switzerland, and Great Britain.
WHY: Luther did not agree with Church practices that allowed wealthier followers to buy indulgences, which were essentially Catholic "get out of jail free" cards. Calvin believed in a religion that stressed God's power, rather than the power of men within the church, and predestination, which was a belief in fate over free will. King Henry wanted his marriage to Catherine of Aragon dissolved so that he could remarry and try to get a male heir. The pope refused to grant an annulment, so Henry created his own church.
HOW: Luther wrote and posted his 95 Theses, which led to a revolt and eventually the creation of Lutheranism, an offshoot of Catholicism that encouraged a "priesthood of all believers". Calvin began his practice by invitation and developed a huge following, who then spread his word to many other countries. Henry integrated accessible Bibles into every parish, and after his death the country went back and forth between Calvinism and Catholicism until the reign of Elizabeth I in 1559.