What is the difference between the Old Testament and the New Testament? Who wrote them? When were they written? The OT and the NT seem to confuse me.
Most Christians believe that the main difference between the Old and New Testaments is that the Old Testament looks forward to the coming of the Messiah (Christ), while the New Testament tells of his coming and the spread of the good news that he came to save the world from sin. The Old Testament tells of the history of the Jews, from the creation to the Covenant with God called the Law of Moses, to the destruction and restoration of the nation. It includes prophecies of the coming of the Messiah. The New Testament tells that the son of God came to die as a sacrifice for sin, that all men (not just the Jews) could take advantage of that sacrifice, and the history and beliefs of the kingdom he established (the church).
That is a pretty simplified description of the differences.
About 60 men, of some of whom we know the names, wrote the Bible. The oldest book of the Bible is probably Job, which may have been written as early as 1300 BC. Most of the Old Testament was written between 800 and 500 BC. The New Testament was written between about 45 and 90 AD. For more details, check out a good book on the subject, like How Came the Bible, by Edgar J. Goodspeed.