What is the real meaning of the kingdom? A kingdom is a rule, a government, and the kingdom of God simply means the rule and government of God. From eternity to eternity God is the King, the sovereign almighty Ruler of the whole universe. The entire universe from eternity to eternity is the kingdom of God. According to Ezekiel 28:11-19 and Isaiah 14:12-20, one of the archangels, Lucifer, rebelled against God, and a number of the angels followed him in his rebellion (Rev. 12:3-4). After the creation of man, Lucifer or Satan came to induce man to rebel also. Due to these two rebellions—that of Satan with his angels and that of man—the ruling and government of God has been greatly interrupted, tested, and attacked. Instead of being under the rule and control of God, the earth has come under the rule and control of Satan and fallen man. This is the earthly kingdom. By the time the Lord Jesus came to the earth at His incarnation, nearly the whole earth was the kingdom of the earth, controlled by Satan and by man. The Lord Jesus came to work out God's intention of bringing His kingdom into this world. God's intention is to have the earth controlled by the heavens. For this reason He needs to bring His kingdom to the earth. The whole earth needs to be brought under a heavenly rule and government. The Lord Jesus came to bring the earth under the control of the kingdom of the heavens.
This is why John the Baptist cried, "Repent, for the kingdom of the heavens has drawn near" (Matt. 3:2). Men needed to repent and to come under the heavenly rule. When the Lord Jesus came with the kingdom of the heavens, He was rejected by the Jewish people; so He turned to the Gentiles and established His church among the Gentiles. Within the church He brought all things under the control and government of the heavens. In the church there is the heavenly rule and government, and there is the reality of the kingdom of the heavens. During the period of the church age, however, the kingdom of the heavens, the heavenly rule, is not manifested in an open way. Rather, it is a heavenly rule in a very mysterious and hidden way. Although it is not yet manifested, the reality of the heavenly rule is present. In the church at least some of the Christians are under the ruling of the heavens. With them there is the reality of the kingdom of the heavens.
When the Lord Jesus comes back, He will subdue the whole world and the kingdoms of this world will become the kingdom of our Lord. At that time the kingdom of the heavens will be manifested in an open way (Rev. 11:15). The kingdom of the heavens will become the ruling power and will govern in a manifested, open way, not in a mysterious and hidden way. Now the kingdom of the heavens rules within the church in a hidden, mysterious way, but at that time the kingdom of the heavens will be fully manifested. The kingdom of the heavens simply means the heavenly rule and government. If you are in the reality of the kingdom of the heavens, you are under the control and rule of the heavens.