Even though the vast majority of churches that trace back their history to Calvin (including Presbyterians, Congregationalists, and a row of other Calvinist churches) do not use it themselves, since the designation "Reformed" is more generally accepted and preferred, especially in the English-speaking world.
The movement was first called Calvinism by Lutherans who opposed it referring to French reformer John Calvin, and many within the tradition would prefer to use the word Reformed. The biggest Reformed association is the World Communion of Reformed Churches with more than 80 million members in 211 member denominations around the world. It was first used by a Lutheran theologian in 1552.
Early influential Reformed theologians include Ulrich Zwingli, John Calvin, Martin Bucer, William Farel, Heinrich Bullinger, Peter Martyr Vermigli, Theodore Beza, and John Knox. Gresham Machen, Karl Barth, Martyn Lloyd-Jones, Cornelius Van Til, and Gordon Clark were influential. It was a common practice of the Catholic Church to name what they perceived to be heresy after its founder.
Calvinists differ from Lutherans on the real presence of Christ in the Eucharist, theories of worship, and the use of God's law for believers, among other things.
As declared in the Westminster and Second Helvetic confessions, the core doctrines are predestination and election. Keller, John Piper, David Wells, and Michael Horton.
Each of these theologians also understood salvation to be by grace alone, and affirmed a doctrine of particular election (the teaching that some people are chosen by God for salvation).
Martin Luther and his successor Philipp Melanchthon were undoubtedly significant influences on these theologians, and to a larger extent later Reformed theologians.
This and the Belgic Confession were adopted as confessional standards in the first synod of the Dutch Reformed Church in 1571.
Leading divines, either Calvinist or those sympathetic to Calvinism, settled in England (Martin Bucer, Peter Martyr, and Jan Łaski) and Scotland (John Knox).
The protestant part of this reformation was considering that the Bible be interpreted by itself, meaning the parts that are harder to understand are examined in the light of other passages where the Bible is more explicit on the matter. Reformed churches may exercise several forms of ecclesiastical polity; most are presbyterian or congregationalist, though some are episcopalian.
The term Calvinism can be misleading, because the religious tradition which it denotes has always been diverse, with a wide range of influences rather than a single founder. Calvinism is largely represented by Continental Reformed, Presbyterian, and Congregationalist traditions.
Calvin did not live to see the foundation of his work grow into an international movement; but his death allowed his ideas to break out of their city of origin, to succeed far beyond their borders, and to establish their own distinct character.