In order to reveal Himself to men, in the condescension of His goodness God speaks to them in human words: “Indeed the words of God, expressed in the words of men, are in every way like human language, just as the Word of the eternal Father, when He took on Himself the flesh of human weakness, became like men” 

Dei Verbum quoted in CCC 101

We are surrounded with dualities in life. A duality is when one thing has two (sometimes more, which would be called a plurality) natures. For example, a person could be both a daughter and a sister at the same time. She has both roles in her life, and neither cancels the other out. She does not stop being a sister when she is a daughter, nor does she stop being a daughter when she is a sister. Similarly, Scripture is both the Word of God and the words of humans, and Jesus Christ is both fully God and fully man.

It is part of human experience for things to have multiple natures at the same time. This helps us better understand how scripture is both the Word of God and the words of humans, and Jesus Christ is both fully God and fully man.

Sacred Scripture is the speech of God as it is put down in writing under the breath of the Holy Spirit.

Catechism of the Catholic Church 81