The simplest answer to this question is to say that Catholics believe that there is a God who loves us and cares for us like a loving Father; a God who nourishes, strengthens and guides us; a God of immeasurable mercy who became one with us so that we might become one with God.
This God was revealed to us by Jesus Christ, who claimed that He was the one, true messenger, and that His task was to announce and establish God’s kingdom on earth.
Catholic beliefs are succinctly expressed in the profession of faith or credo called the Nicene Creed:
I believe in one God, the Father almighty, maker of heaven and earth, of all things visible and invisible.
I believe in one Lord Jesus Christ, the Only Begotten Son of God, born of the Father before all ages.
God from God, Light from Light, true God from true God, begotten, not made, consubstantial with the Father;
through him all things were made.
For us men and for our salvation he came down from heaven, and by the Holy Spirit was incarnate of the Virgin Mary, and became man.
For our sake he was crucified under Pontius Pilate, he suffered death and was buried, and rose again on the third day in accordance with the Scriptures.
He ascended into heaven and is seated at the right hand of the Father.
He will come again in glory to judge the living and the dead and his kingdom will have no end.
I believe in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father and the Son, who with the Father and the Son is adored and glorified, who has spoken through the prophets.
I believe in one, holy, catholic and apostolic Church.
I confess one Baptism for the forgiveness of sins and I look forward to the resurrection of the dead and the life of the world to come.
Our faith teaches us to Love God. To love God is to make Him and His will the center of our lives. And our faith teaches us to Love our neighbour. That means to practice what God taught, and modeled, for us through Jesus Christ. The Gospels teach us that love is giving without expecting repayment, helping without expecting anything in return. Loving our neighbour means helping in any way anyone who needs help.
The Catholic Church is a sacramental faith facilitating a personal connection with God. We can experience that ongoing encounter through what Christ gave us - the Church and the Sacraments, especially the Eucharist. At the most basic level, the purpose of the Church is to provide the “Way” to know and practice that faith to fulfil our obligations to God and our neighbour.