If one is to properly understand the message of the Bible, he or she must first understand how the Bible is structured. We need to be able to read the Bible's "blueprint".
Two major sections
The books of the Bible are separated into two major sections. The first 39 books are contained within what is referred to as the Old Testament. The remaining 27 books are in the New Testament. The books of the Old Testament were written in the Hebrew and Aramaic languages. The New Testament books were all written in Greek.
The Old Testament books cover the period of time from the creation of the world until about 425 B.C. There are books of history, poetry and prophecy. The first five books of the Old Testament were written by Moses in about 1450 B.C. The other 34 books in the Old Testament were written by a number of other people over the following 1000 years. The Old Testament's primary focus is on God's dealings with the descendants of Abraham (the Israelites/Jews).
The New Testament books record events in the first century A.D. that pertain to the life of Jesus Christ and the establishment of His group of disciples (also known as the church). There are five books of history, 21 letters (books) written to Christians and one book of prophecy.
The Convenants of the Bible
The word "testament" is an older term for the word covenant. A covenant is not really the same thing as our modern "contract", but there are similarities; both are agreements between two parties. One of the most well known covenants was between God and the Israelite nation. It was the first of two great covenants which God has given to man and therefore is referred to as the "Old Testament" since people today are bound by the agreement of a New Covenant. The Old Covenant was national rather than universal; it only applied to the ancient Israelites who were the descendants of a man named Abraham. The laws of this covenant where given by God to Moses on Mount Sinai and contained not only the Ten Commandments, but also detailed information about every aspect of the life and worship of the ancient Jewish people. The writings of the Old Testament are collectively referred to as "The Law" or "The Law of Moses".
While the Old Testament was given through Moses and was directed only to the Jews, the New Covenant came through God's Son, Jesus Christ. The New Covenant took effect when Jesus died on the cross (Hebrews 9:15-17). The New Testament writings contain instructions which tell people today how to be forgiven of our sins and to live a life that is pleasing to God.
Since the death of Jesus Christ, the Old Testament is no longer in effect and we are not bound by its laws and requirements today. The requirements under the new covenant are not the same as those under the old covenant. It is true that there are things that both testaments have in common, but we don't obey them because they are found in the Old Testament writings. We obey them because they are found in the new covenant writings.
The time period prior to the first covenant that God made with the Jewish nation is commonly referred to as the Patriarchal Age. This is because God dealt directly with the male heads of families (patriarchs).
Correctly handling the word of truth
As Bible students, we must make a distinction between the laws and commands that God gave to people of other ages and the ones that He expects us to obey today. For example, God once commanded Noah to build an ark to save himself and his family. This was a command given to one man for a specific reason and God never intended anyone else to obey this directive. It is recorded in the Bible to teach us. Likewise, under the old covenant, the ancient Israelites were not permitted to wear garments made of "mixed linen and wool" (Leviticus 19:19) but this is not a prohibition under the new covenant. Many examples such as these could be referenced but the point is that many commands given by God were never intended to be obeyed by all people of all times.
In 2 Timothy 2:15 the Bible says, "Do your best to present yourself to God as one approved, a workman who does not need to be ashamed and who correctly handles the word of truth." This verse is teaching us to be careful and diligent to correctly interpret the message of the Scriptures. We must "correctly handle" the Bible in order to determine which laws we are to obey today and which ones were given to other people of other times.