Question: "What is infralapsarianism, supralapsarianism, and sublapsarianism?"
Answer: These three theological terms deal with Godís predestination of certain individuals to be saved. The focus of infralapsarianism, supralapsarianism, and sublapsarianism is the order in which God determined things to happen. In what order did God create humanity, allow the fall, elect some to salvation, and provide salvation for humanity? Ultimately, these are issues that we are incapable of fully grasping. It does not truly matter what order God decreed what to occur. What truly matters is that God created humanity, humanity sinned, and God decided to provide salvation through Jesus Christ.
Infralapsarianism puts Godís decrees in the following order: (1) God decreed the creation of mankind, (2) God decreed mankind would be allowed to fall into sin through its own self-determination, (3) God decreed to save some of the fallen, and (4) God decreed to provide Jesus Christ as the Redeemer. Infralapsarianism focuses on God allowing the fall and providing salvation.
Sublapsarianism is very similar to infralapsarianism, putting Godís decrees in the following order: (1) God decreed to create human beings, (2) God decreed to permit the fall, (3) God decreed to provide salvation sufficient to all, and (4) God decreed to choose some to receive this salvation. The only difference between infralapsarianism and sublapsarianism is whether God decreed to provide salvation through Jesus Christ and then decreed to choose some to be saved, or vice-versa.
Supralapsarianism puts Godís decrees in the following order: (1) God decreed the election of some and the eternal condemnation of others, (2) God decreed to create those elected and eternally condemned, (3) God decreed to permit the fall, and (4) God decreed to provide salvation for the elect through Jesus Christ. Supralapsarianism focuses on God ordaining the fall, creating certain people for the sole purpose of being condemned, and then providing salvation for only those whom He had elected.
GotQuestions finds infralapsarianism to be the most biblical position. We do not believe the Bible portrays God as decreeing the fall and creating people for the sole purpose of eternal condemnation. Supralapsarianism results in the doctrine of limited atonement (Jesus died only for the elect). Supralapsarianism is typically the view of 5-point Calvinists, while infralapsarianism and sublapsarianism are usually held by 4-point / moderate Calvinists. Ultimately, though, these are issues best left up to God. Instead of worrying or arguing over when God decreed what, our concern should be on proclaiming the Gospel of Jesus Christ to all who need to hear it.