Huguenots were French Protestants during the Reformation in France and in some places still are today. They have been heavily persecuted throughout French history by various groups and often by the state, and their numbers have never been as high as they were before the French Wars of Religion. 

The Council of Trent convened in the middle of the sixteenth century. Its purpose was to provide an official Catholic response to the Protestant Reformation. In particular, the Council ruled on the various doctrines of faith that were being criticized by the Protestant Reformation and widely reaffirmed them. It also ruled that Bishops had to be present in the territory that they governed and that the sale of indulgences was an illegal church practice.

The Peace of Augsburg was signed in 1555 between Charles V, the head of the Holy Roman Empire, and an alliance of Lutheran Princes. The Peace formally ended hostilities between the two groups and permanently established the division of Christianity between Catholicism and Protestantism in the Holy Roman Empire. Although it provided some measure of "religious tolerance," to use that phrase suggests far more tolerance than was present at the time. Yes, the rulers of a princely state could determine which form of Christianity they wanted, but all their subjects had to obey on pain of death, and executions and genocides remained common throughout Europe.

The Defenestration of Prague occurred in 1618. It refers to an incident where a group of Catholic Lords were thrown out of a window following a rather heated disagreement with a group of Protestants. This incident is one of the most famous in the build-up to the Thirty Years' War, which would rage from 1618 until 1648 across much of Central Europe. 

In Anglicanism, the English monarch is head of the Church of England. In Anabaptism, adults are baptized rather than babies. Predestination, the belief that people's eternal fate is predetermined by God before they are born, is a core concept of Calvinism. Justification through Faith alone is the crucial difference between Lutheranism and Catholicism. Luther said that good works and following the rules of the Church were not the way through which eternal salvation was achieved. Instead, Luther argued that salvation was already promised, all one had to do was believe in it and have faith in Christ's saving grace. 

The Pope, and the Catholic Church, has the right to "excommunicate" individuals or entire nations from the church. This essentially means that the individual or the people of the nation are blocked off from salvation. The Pope might excommunicate a nation in order to put political pressure on a European monarch. If the common people follow the Catholic faith and suddenly believe that their path to eternal salvation has been blocked by the intransigence of their King, they would be likely to break out in open rebellion rather than suffer eternal damnation. 

The Thirty Years' War began as a conflict between Catholics and Protestants in the weakening Holy Roman Empire. It quickly spread, however, to engulf almost all the major powers in Europe. The Thirty Years' War is often remembered as one of the most brutal wars in European history. It devestated Central Europe and decimated the populations of modern-day Germany and the Low Countries.