Jesus, who was the Son of God, and God the Son, emptied Himself of His Godly attributes and came as a baby into the fleshly world of men. Jesus was a new creation. The first time in all of history that God became flesh. When he did that, he really did it. It wasn't pretend... it wasn't symbolism, it was real and true. God the Son is no more. Now, and forevermore, there is Jesus Christ.
And He died on the cross for our sins. Who died? Jesus, the Son of God, God the Son, died on the cross.
So, what is death? Death is separation from God. When Adam ate of the fruit, God said
"for in the day that you eat of it you shall surely die." Adam did not go to the grave on that day, but he did die. He became separated from God on that day.
So, when we say that God the Son, who is now Jesus Christ, died on the cross we are not saying that he ceased to exist (as Knight has stated so aptly already in this post). No, we are saying that He was separated from God the Father and God the Holy Spirit. It was the first time the Trinity had been separated and it was terrible for the Father, Jesus (the Son), and the Holy Spirit. it was a true price paid, with the attendant consequences of sin, which Jesus became for us.
Christ then went to hell to (a) Proclaim to the fallen angels in hell that their plan to stop the incarnation had failed;
1Pet 3:18-20 For Christ also suffered once for sins, the just for the unjust, that He might bring us to God, being put to death in the flesh but made alive by the Spirit, by whom also He went and preached to the spirits in prison, who formerly were disobedient,
and (b) to take the believers in Abraham's Bosom from Hades to heaven.
Ephesians 4:8-10 Therefore He says: “ When He ascended on high, He led captivity captive, And gave gifts to men.” (Now this, “He ascended”—what does it mean but that He also first descended into the lower parts of the earth? He who descended is also the One who ascended far above all the heavens, that He might fill all things.)
Knight asked a great question; Where was God the Son when Jesus died on the cross? The answer is that they are one and the same. God the son became flesh (Jesus Christ) and was forever changed. God and man as one. Death is separation. Jesus was separated from the Godhead but was reunited because He was righteous.
