What
Everything God has promised, Place of security.
To be saved implies that one is in danger, or is in a place of captivity, therefore it is necessary to understand from what one is being saved and simultaneously to what.
The from is the captivity and condemnation of our blindness of who we are (i.e. children of the Most High God > gods ourselves Psalm 82:6, John 10:34).
So the to is being set free to see ourselves as true children of God (open the eyes of our hearts / Let the light of life shine). Our salvation sets us free from the captivity and condemnation of Satan, Sin and Death, to Truth, Righteousness and Life, and is guaranteed for eternity. There is therefore no condemnation. Our place of security has always been one with our Father God (John 14:20, John 17:20-23).
Why
God’s love for all (John 3:16), recognised or not by the individual (1 Tim 4:10). For having been made in His image & likeness it was necessary for Him to redeem that image. In Genesis 1:28 God commands Adam to subdue his earth and he would then have dominion over it. Yet we find in Genesis chapter 3 that Adam/Eve allows the desires of their flesh (their earth) to subdue them and thus blinds them to their true nature and gives dominion to Satan. So God then requires another to subdue the earth to regain the dominion lost. This one is Jesus, the last Adam (1 Cor 15:45), and in John 16:33 he declares that “he has overcome the world”, or paraphrased as “I have subdued your earth”! And then John in 1 John 5:4 emphasizes that fact.
When
From the beginning, before time. Our default condition was reset on the cross (in His words on the cross – “It is finished”, both His act of redemption and our self-proclaimed guilt), and the proof of our oneness with the Father by the resurrection. Although we have died in Jesus, were crucified and descended to Hades in Him, and have risen in Jesus to heavenly places, unless we come to that realisation, we cannot fully experience the fullness of our true position in God now (1 Tim 4:10).
How
The Cross; victory over death and sin. Jesus becomes the example OF humanity, not FOR humanity. He is the completed fulfilment of humanity. And then re-activated His Holy Spirit in ALL humanity (Acts 2:16-17; Joel 2:28-29)
Who
For all humanity since creation, but the most benefit is to be gained by those who choose to accept this great good news now (1 Tim 4:10).