Presbyterianism is a Reformed (Calvinist) Protestant tradition named for its form of church government by representative assemblies of elders. Though there are other Reformed churches that are structurally similar, the word Presbyterian is applied to churches that trace their roots to the Church of Scotland or to English Dissenter groups that formed during the English Civil War.
Iona Abbey in Scotland was founded by Saint Columba
John Knox
The Ordination of Elders in a Scottish Kirk, by John Henry Lorimer, 1891. National Gallery of Scotland.
Celtic cross draped for Easter at a Presbyterian church
Reformed Christianity, also called Calvinism, is a major branch of Protestantism that began during the sixteenth-century Protestant Reformation, a schism in the Western Church. In the modern day, it is largely represented by the Continental, Presbyterian, and Congregational traditions, as well as parts of the Anglican and Baptist traditions.
Statues of William Farel, John Calvin, Theodore Beza, and John Knox, influential theologians in developing the Reformed faith, at the Reformation Wall in Geneva
Calvin preached at St. Pierre Cathedral in Geneva.
Early Calvinism was known for simple, unadorned churches as depicted in this 1661 portrait of the interior of the Oude Kerk, Amsterdam
Fall of Man by Jacob Jordaens