TULIP is the theology that emerges from Calvinism. It basically refers to the plan of salvation.
T = Total Depravity. The theological idea of total depravity basically refers to the sinfulness of man. According to this framework, humans are “dead” to the things of God. As Ephesians 2:1 states, “You were dead in your sins and transgressions.” For this reason, according to this framework, a person cannot choose God.
U = Unconditional Election. The corollary of total depravity is unconditional election. In other words, if people cannot choose God, then God must do the choosing. Moreover, if people are dead to God, then there is nothing in humanity that God views as the basis for merit for divine election. Hence, God’s election is unconditional, that is, not based on people. For example, Ephesians 1:4 states that people were chosen before the foundations of the world. The time of election is significant, because election occurs before people do any right or wrong.
L = Limited Atonement. Limited atonement, which is sometimes called particular atonement, states that the second person of the trinity came to die for only the elect. The rationale for this is simple. The atonement is completely efficacious. The other option is the atonement only provides the potentiality of salvation.
I = Irresistible Grace. Irresistible grace speaks of the work of the Holy Spirit. Those whom the father has elected and for whom the son has atoned, the Holy Spirit quickens to have faith in Christ. There is a new heart with new affections for Christ.
P = Perseverance of the Saint. This point refers to the fact that God’s grace will sustain a person to the end. In other words, God’s grace will enable people to persevere to the end irrespective of the hardships. According to this theological framework, people persevere, because God perseveres.