Traditionally, one was called a Calvinist for following the teachings of John Calvin, a 16th-century magisterial Reformer and theologian. Calvin emphasized the sovereignty of God, the unconditional election of the saved, and the irresistible grace that saves a sinner.
The “Five Points of Calvinism” are often referred to in discussions of Calvinism and whether or not one is a Calvinist. The five points of Calvinism are summarized in the acrostic TULIP: T = Total Depravity, U = Unconditional Election, L = Limited Atonement, I = Irresistible Grace, and P = Perseverance or Preservation of the Saints. Some people identify themselves as full, or five-point, Calvinists; others see themselves as four-point Calvinists, etc., based on the degree to which they accept the various doctrines in TULIP. However, all Calvinists agree with the teaching of unconditional election. The doctrine of election is the teaching that God chooses whom He is going to save according to His own desire and for His own reasons without taking into account the actions, attitudes, or decisions of the sinner being saved.
The most common variant from a five-point Calvinist is what is often referred to as a four-point Calvinist. This is someone who rejects the L (Limited Atonement) in TULIP. The doctrine of limited atonement teaches that Jesus’ death on the cross only atoned for the elect—He did not die for the whole world but only for those who would be saved. Four-point Calvinists, who reject this teaching, believe in what is called universal or unlimited atonement. In their view, Jesus’ death was sufficient to atone for the sins of everyone who ever lived or will live, but it only applies to those who come to saving faith in Jesus.
Some see Calvinism as a term synonymous with Reformed Theology. While there are definite associations, Reformed theology is a broader set of theological ideas that go beyond the doctrine of salvation. Reformed theology is also often associated with covenant theology. Not everyone who identifies as a Calvinist would claim the “Reformed” label, and many Calvinists reject covenant theology.
Calvinists take the Bible to be the literal Word of God, and they emphasize the sovereignty of God in the world’s affairs, especially the salvation of sinners. Salvation is all of God, says the Calvinist, and those who are saved are the grateful recipients of divine grace.