Jesus Christ is true God and true man. He is not part God and part man. He is not the result of a confusion or mixture of the divine and human. Jesus Christ was truly a man in all respects while remaining truly God in all His Divine Nature.
Christ is Son of God by nature and not by adoption. The Son of God is begotten not made and is of the same substance as the Father. The Word united to himself in His person the flesh animated by a rational soul and became truly a man. Christ’s humanity has no other subject than the divine person of the Son of God who assumed humanity and made it His own from His conception. This is why Mary is called the Mother of God.
The Council of Chalcedon in 451 further clarified the truth of Christ.
Following the holy Fathers, we unanimously teach and confess one and the same Son, our Lord Jesus Christ: the same perfect in divinity and perfect in humanity, the same truly God and truly man, composed of rational soul and body; consubstantial with the Father as to his divinity and consubstantial with us as to his humanity; "like us in all things but sin". He was begotten from the Father before all ages as to his divinity and in these last days, for us and for our salvation, was born as to his humanity of the virgin Mary, the Mother of God.
We confess that one and the same Christ, Lord, and only-begotten Son, is to be acknowledged in two natures without confusion, change, division or separation. the distinction between the natures was never abolished by their union, but rather the character proper to each of the two natures was preserved as they came together in one person (prosopon) and one hypostasis.
Everything in Christ’s human nature is to be attributed to his Divine person as its proper subject, not only His miracles but also His sufferings and even His death. Jesus is inseparably true God and true man. He is truly the Son of God who without ceasing to be God and Lord became a man and our brother.
Christ assumed, not absorbed, human nature in the Incarnation. Christ has a human soul with its operations of intellect and will and of His human body. Christ’s human nature belongs as His own to the divine person of the Son of God who assumed it. Everything that Chris is and does in this nature derives from one of the Trinity. The Son of God worked with human hands, thought with a human mind, acted with a human will, and loved with a human heart. Born of the Virgin Mary, He has truly become one of us, like us in all things except sin.
While truly God, Christ, the eternal Son, also assumed a rational, human soul. His human soul is endowed with a true human knowledge. As such, this human knowledge could not in itself be unlimited. It was exercised in the historical conditions of his existence in space and time. The Son of God grew in wisdom and in stature, and in favor with God and man. Christ would even have to inquire for Himself about what one in the human condition can learn only from experience.
Christ’s human knowledge expressed the divine life of His person. His human nature by virtue of its union with the Word knew and revealed in itself everything that pertains to God. The Son of God made man has intimate and immediate knowledge of His Father. The Son in His human knowledge showed the divine penetration He had into the secret thoughts of human hearts. Christ in His human knowledge had a fullness of understanding of the eternal plans He had come to reveal.
As true God and true man, Christ possesses two wills and two natural operations – divine and human. These are not opposed to each other but cooperate such that Christ willed humanly in complete obedience to His Father all that He had decided divinely with the Father and Holy Spirit for our salvation. His human will submits to His divine and almighty will.
In assuming a true humanity, Christ’s body was finite. The individual characteristics of Christ’s body express the divine person of God’s Son. The Son has made the features of his human body His own. This is the source of the use of Icons and images of Jesus among the faithful in the Catholic and Orthodox Christian traditions.
Jesus Christ knew and loved throughout His earthly life. He loved with a human heart with a love with which He continually loves the eternal Father and all humans without exception. Through Him and His love, we are lifted into the very Heart of the Father in the Holy Spirit. Christ fully assumed our humanity so that we may fully share in His Divine Life.
Summary of the Cathechism of the Catholic Church paragraphs 464 - 478