The text of the Old Testament was written in Hebrew and Aramaic over a period of approximately 1,000 years, beginning with Moses and extending to the Persian period following the Jews’ return to Judah from exile. It’s an ancient book with the oldest parts written some 3,500 years ago. This means parts of it will be difficult for people today to understand.
The New Testament books were written in the first and second century AD in Greek, with the last book written no later than AD 150. The New Testament tells us about Jesus Christ and the early Christian church, and presents Christianity’s main teachings.
The writings of both Testaments were carefully preserved and meticulously copied word for word over the years, until the invention of the printing press made it much simpler to duplicate.