Q. 1. I heard the term "Canon of Scripture." What does that mean?
A. 1. The Compendium of the Catholic Church defines the Canon of Scripture (also known as the "canon of Sacred Scripture.") as the complete list of the sacred writings which the Church has come to recognize through Apostolic Tradition. The Canon consists of 46 books of the Old Testament and 27 of the New Testament.
In simple words, the Canon of Scripture consist of all the Books and Letters that belong to the Holy Bible as inspired by the Holy Spirit. There are 46 books in the Old Testament and 27 books or letters in the New Testament. In total, the Canon of Scripture (the Bible) has 73 books / letters.
The Protestant Churches that have rejected 7 books from the Holy Bible, for a different total of only 66 books, they do not enjoy the fullness of the Canon of Scripture as inspired by the Holy Spirit. They have partially rejected what the Holy Spirit gave to the Church. In other words, they have partially rejected the work of God.