Members of the LDS Church don’t talk much about what happens in the temple. As is often said, we regard these things as sacred. I submit at the time the endowment was introduced there was also a need for secrecy, since it was not known who was true and who was traitor.
The ceremonies of the temple involve preparation to become servants of God. The instructions given and covenants made in the temple are towards this end of preparing individuals for eternal life.
As discussed in the Bible and argued by Jesus in John 10: 34-38, the Jewish law taught that mortals could become gods. 1 The purpose of the temple would be to allow individuals to enter into those covenants and perform those ordinances that would prepare them to becomes the gods the Bible speaks of, holy beings who serve God, the Father of all. These individuals would, if faithful, reign and minister in God’s heaven.
The instructions form a basis for understanding God’s work and salvation: our existence before mortality, the fall of Adam and Eve, the purpose of our mortal lives, the reality of resurrection after this life, and the possibility of returning to live with God in his kingdom. 2