The kingdom of Christ, now present in the mystery, grows visibly through the power of God in the world. The Church is identical with the kingdom of Christ. This ideal will come to the fore again when we note Joseph’s part in helping Jesus found the kingdom of God even though that kingdom was the germ at Nazareth-“present in mystery,” in the words of the Second Vatican Council, all the more at Nazareth in the mystery of the eternal plan to introduce the Word Incarnate into the world.
The Constitution on the Church gives some of the metaphors used in scripture to explain this kingdom. It is called a sheepfold, a piece of land to be cultivated, the building of God, the family of God, the true vine who gives life to the branches and power to bear fruit, to us who through the Church remain in Christ, comes the knowledge that without Christ we can do nothing.
Paragraphs 3 and 6 of Constitution of the Church