In simplest terms, the Old Testament is the part of the Bible that was written before the birth of Christ. It includes 39 books, between Genesis and Malachi. The New Testament is the part of the Bible written after the Jesus’ death, burial, resurrection and return to heaven. It is the 27 books starting from Matthew and ending with the book of Revelation.
More specifically, the Old Testament begins with the book of Genesis which tells about the creation of the world, the introduction of sin and God’s choosing of Abraham’s family to be a special people for Himself. The rest of the Old Testament (except the book of Job), tells about the Israelites, Abraham’s descendants, and God’s dealings with them. The New Testament begins with the four gospels, Matthew, Mark, Luke and John, which tell of Christ’s birth, life, execution and resurrection. The rest of the New Testament (except the book of Revelation) is the history of the beginning of the church and letters written to some of the first churches and pastors. The book of Revelation tells of the end of the church age and of God’s final judgments on the world, Satan and all unbelievers.
Of course, with anything as important and influential as the Bible, there are some wrong ideas about the Old and New Testaments that many people think are true. For example, some people think the Old Testament shows a God that is all about wrath and judgment and the New Testament shows a God that is all about love and grace. This idea has gained such strength that some people actually believe the God of the Old Testament is different from the God of the New Testament. This is absolutely not true. The God of the Old Testament is a God of love and wrath, just as is the God of the New Testament. For example, the book of Song of Solomon is a beautiful picture of God’s love for his people. The book of Exodus is all about how God in his love rescued the Israelites from their slavery in Egypt. In the New Testament, an entire book, the book of Revelation, describes the coming pouring out of God’s wrath on mankind. The Bible, though it has two testaments and many individuals books, is one Book telling of the one God and His work to redeem a people to Himself for His glory.
Another wrong idea that people have is the belief that the Old Testament doesn’t really matter anymore. Some people write it off as if it’s nothing more than ancient history, or untrue stories that don’t have any real application for us today. God tells us, through the apostle Paul in Romans 15:3 that the things which are written in the Old Testament are for our learning, that through the Scriptures we will have comfort and hope. The Old Testament really does matter for us today showing us how God deals with His people, teaching us much about the character and work of God, and giving us many examples of how we should live today.
The Old and New Testaments are both equally the Word of God. They are written for our benefit and they teach us about God, His work to save people from their sin and His eternal plans for His glory. The Old and New Testaments are different primarily because of their relationship to Christ, the one before and the other after, and because of the different people being discussed, the Israelites in the Old and the church in the New. Though the testaments are different, they are part of the same story unfolding the great work of God “to the praise of the glory of His grace.”