The fundamental beliefs and teachings of the Catholic Church are rooted in the teachings of Christ and those of his Twelve Apostles. The best summary of our beliefs is found in the Nicene-Constantinopolitan Creed from 381 AD.
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.
Some of the major sources on Catholic Church teachings include:
Catechism of the Catholic Church (Vatican)
Code of Canon Law (Vatican)
U.S. Catholic Catechism for Adults (USCCB)
Compendium of the Social Doctrine of the Church (USCCB)
The Roman Missal
General Instruction of the Roman Missal
The Rite of Baptism
The Order of Celebrating Matrimony
Pastoral Care of the Sick and Dying
The Rite of Confirmation
The Rite of Ordination
The Rite of Penance
The Rite of Christian Initiation of Adults
The documents of the Second Vatican Council
The documents from other preceding Church Councils
Synods of Bishops
Publications by the Acta Apostolicae Sedis (Vatican)
Encyclicals, Exhortations, Constitutions and moto proprios of the popes
Documents published by the USCCB