Question: "What is the Kingdom of God?"
Answer: The kingdom of God is the rule of an eternal sovereign God over all creatures and things (Psalm 103:19; Daniel 4:3). The kingdom of God is also the designation for the sphere of salvation entered into at the new birth (John 3:5-7), and is synonymous with the “kingdom of heaven.”
The kingdom of God embraces all created intelligence, both in heaven and earth that are willingly subject to the Lord and are in fellowship with Him. The kingdom of God is, therefore, universal in that it includes created angels and men. It is eternal, as God is eternal, and it is spiritual—found within all born-again believers. We enter the kingdom of God when we are born again, and we are then part of that kingdom for eternity. It is a relationship "born of the spirit" (John 3:5), and we have confident assurance that it is so because the Spirit bears witness with our spirits (Romans 8:16).
God is sovereign, omnipotent, omniscient and the ruler over all of His creation. However, the designation "the kingdom of God" compasses that realm which is subject to God and will be for eternity. The rest of creation will be destroyed. Only that which is part of the "kingdom of God" will remain.