The Kingdom of God

Seek first the kingdom (of God) and his righteousness, and all these things will be given you besides. (Matthew 6:33)

Different meanings of the Kingdom of God:

The kingdom of God refers to heaven, where the blessed will live with God forever, even after the world has passed away.

The Kingdom of God is brought near in the Word incarnate, it is proclaimed throughout the whole Gospel, and it has come in Christ’s death and Resurrection. The Kingdom of God has been coming since the Last Supper and, in the Eucharist, it is in our midst. The kingdom will come in glory when Christ hands it over to his Father. (CCC 2816)
At the end of time, the Kingdom of God will come in its fullness. Then the just will reign with Christ forever, glorified in body and soul, and the material universe itself will be transformed. God will then be “all in all” (1 Cor 15:28), in eternal life. (CCC 1060) After the universal judgment, the righteous will reign forever with Christ, glorified in body and soul. The universe itself will be renewed. (CCC 1042)

The kingdom of God refers to Jesus Christ Himself.

In Jesus “the Kingdom of God is at hand.” Jesus said: “The kingdom of God is at hand. Repent, and believe in the gospel.” (Mark (NAB) 1:15) According to Pope Benedict XVI in his book “Jesus of Nazareth,” when Jesus speaks of the Kingdom of God, He is quite simply proclaiming God, and proclaiming Him to be the living God, who is able to act concretely in the world and in history. This is the hour when God is showing himself in history as its Lord in a way that goes beyond anything seen before. (pp. 55-56)
The kingdom of God is present in principle in Jesus Himself, inasmuch as He perfectly cooperates with the Father and the Holy Spirit in His preaching and miracles. But also inasmuch as He perfectly obeys the Father, He also makes God’s reign present by everything He says and does.

The kingdom of God refers to God’s saving action.

The Creator who at first had found everything that he made “very good” (Gn 1.31) and who then had for a long time patiently tolerated sin and its consequence was beginning to take action to renew the broken world, and thus was bringing into the world the kingdom of God.
God’s saving action is a process. The process of the coming of God’s kingdom began with the Incarnation of the Word.
Christ’s compassion toward the sick and his many healings of every kind of infirmity are a resplendent sign that “God has visited his people” and that the Kingdom of God is close at hand. (CCC 1503)
From the beginning of his public life Jesus chose certain men, twelve in number, to be with him and to participate in his mission. He gives the Twelve a share in his authority and ‘sent them out to preach the kingdom of God and to heal.” (CCC 551)