This question probably refers to the difference between the books in the Protestant Bible and the Roman Catholic Bible that includes such books as Tobit, Judith, 1 & 2 Esdras and others. In other words, how was the decision made about what books were included or not included in the Bible?
Here is a very brief answer and a couple of resources to study. The books mentioned are part of books that are called "The Apocrypha" (which means "things that are hidden"). These were books that were written between the conclusion of the Old Testament book of Malachi and the opening of the New Testament. That was a period of approximately 400 years. According to one source Jesus and the New Testament authors quote or refer to parts of the Old Testament nearly 300 times but not once do they cite any statement from any of the books of the Apocrypha or any other writings as having divine authority. The books were never accepted by the Jews as Scripture. They were referred to by Jerome in his translation of the Bible into Latin as "books of the church" not "books of the canon (standard)." Also they contain teachings that are inconsistent with the rest of Scripture.
For further reading check out the book, "The Canon of Scripture" by F. F. Bruce or look up the topic "canon of Scripture" in any Bible dictionary.