In Mormonism, the Plan of Salvation is the plan which Heavenly Father created, to save, redeem, and exalt his children (all of mankind are included in his children).

Before we were born, his children lived with Heavenly Father in heaven. Heavenly Father presented this plan to his children - they (we) would go to "an Earth" (used to refer to any habitable planet. There they would receive a physical body (which they did not have at the time - only Heavenly Father had one, as he had already been to "an Earth"), and be tempted and tested. The purpose of this test is not

After Heavenly Father presened this plan, Lucifer presented a different plan, wherein his children would not receive agency, and so noone would fail the test. Thus, everyone would be able to return to live with Heavenly Father. Heavenly Father realized that this would make the test worthless, and so refused Lucifer's plan.

Lucifer then rebelled against Heavenly Father, drawing with him one third of Heavenly Father's children as well. Lucifer became Satan, and those who followed him became fallen, and his servants.