Here’s what the Catechism of The Catholic Church says:
**60 ** The people descended from Abraham would be the trustee of the promise made to the patriarchs, the chosen people, called to prepare for that day when God would gather all his children into the unity of the Church. They would be the root on to which the Gentiles would be grafted, once they came to believe.
1819 Christian hope takes up and fulfills the hope of the chosen people which has its origin and model in the hope of Abraham, who was blessed abundantly by the promises of God fulfilled in Isaac, and who was purified by the test of the sacrifice. “Hoping against hope, he believed, and thus became the father of many nations.”
751 The word “Church” (Latin ecclesia, from the Greek ek-ka-lein, to “call out of”) means a convocation or an assembly. It designates the assemblies of the people, usually for a religious purpose. Ekklesia is used frequently in the Greek Old Testament for the assembly of the Chosen People before God, above all for their assembly on Mount Sinai where Israel received the Law and was established by God as his holy people. By calling itself “Church,” the first community of Christian believers recognized itself as heir to that assembly…
755 "The Church is a cultivated field, the tillage of God. On that land the ancient olive tree grows whose holy roots were the prophets and in which the reconciliation of Jews and Gentiles has been brought about and will be brought about again. That land, like a choice vineyard, has been planted by the heavenly cultivator. Yet the true vine is Christ who gives life and fruitfulness to the branches, that is, to us, who through the Church remain in Christ, without whom we can do nothing.
839 *“Those who have not yet received the Gospel are related to the People of God in various ways.” *
The relationship of the Church with the Jewish People.
When she delves into her own mystery, the Church, the People of God in the New Covenant, discovers her link with the Jewish People, “the first to hear the Word of God.” The Jewish faith, unlike other non-Christian religions, is already a response to God’s revelation in the Old Covenant. To the Jews “belong the sonship, the glory, the covenants, the giving of the law, the worship, and the promises; to them belong the patriarchs, and of their race, according to the flesh, is the Christ”, “for the gifts and the call of God are irrevocable.”