This biographical sketch is part of the article:
Why the Reformation? (T&T 2001) by A E Bouter
John Calvin, a Frenchman by birth, was a second-generation reformer. His name and theology are frequently denoted by the terms 'Calvinism,' 'Reformed Faith,' and 'Presbyterianism.'
My experience has been that most people who are critical of Calvin have never personally read his writings and know very little of the man or his life. In about 1533 he was personally converted to Christ and adopted the ideas of the Reformation. He then gave up his Roman Catholic benefits (income from three parishes, though he was never ordained as a priest; his father, secretary to a bishop, obtained these for Calvin, the first when he was aged six).
With the help of William Farel, Calvin brought his understanding of the Reformation to Geneva, Switzerland, and it spread from there. He emphasized, at the risk of me being overly brief, the sovereignty of God, the total spiritual depravity of the human race, the complete authority of the Bible, and salvation completely as a work of God.
His extant writings total 57 volumes in one printing. Both Calvin and Luther encouraged education, and the later Calvinistic Puritans established many of the oldest colleges and universities in North America. One of the countries into which the Calvinistic Reformation spread was his homeland of France.
Calvinists eventually became so numerous (up to 20% of the population) that the French king, a Roman Catholic, declared war on them. This involved the massacre of many citizens, for example the 'St. Bartholomew's Massacre' in August 1572.