Imagine someone orders a great big pizza. When it is delivered and the box is opened it has been cut into two pieces. Now who can eat that? People are hungry, but they don't want to tear the pizza up.
Then the lady of the house says, "Here, let me cut it up." She uses a pizza cutter to divide the pizza into a bunch of slices. She says, "Now you people can eat it."
This story is really about two ways to understand the Bible. Covenant people divide the Bible into two parts--the Old Testament and the New Testament. Along came the dispensationalists and said, "Lets divide it into smaller pieces." They made finer distinctions and said, "Now you can understand it."
For as we look at the whole Word, and study it as many do, individuals get left out. What about Abraham? Which covenant was he in? Or, Seth? We find there are a number of ways to understand God's dealings with his people, not just two ways.
Before the flood our diet was plant food. After the flood we were told we could eat meat. Dispensations take these changes into account, and other ones too. They add nothing to the Bible, and take nothing out of it. They just divide it into more sections to make it understandable.
Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. 2 Timothy 2:15