Adam and Eve's story is well-known even among the non-Christians. We say that they ate the apple that was forbidden to eta. That is the tree Eve took the fruit from. The tree was the tree of knowledge of good and evil, and it was in the middle of the garden, and God had told Adam clearly that he was not supposed to eat any fruit from it.
Then Adam and Eve was kicked out from the garden of Eden, and an angel came to guard another tree so that no one could come and eat from it. I always assumed that it was the same tree that Adam and Eve took a fruit from . But it was not.
There were two trees in the middle of the garden. I didn't pay any attention to them all these years until my friend called me one day and told me to read this portion of the Bible and paint the picture of the garden of Eden in my mind. But I was supposed to paint only the items that I read from the Bible. Then we can see it.
The Bible says that God planted two trees in the middle of the garden. The tree of life and the tree of the knowledge of good and evil. (Genesis 2:9)
That means that they had been eating from the tree of life because the one tree that they were not supposed to eat from was the tree of knowledge of good and evil. Then they ate from the forbidden tree, and the angel was sent to guard the tree of life, not the forbidden tree.
They couldn't eat from both trees at the same time.. The tree of life gives eternal life.
They couldn't have the knowledge of good and evil and live forever at the same time.
Those who believe Jesus as the Savior will have eternal life. Jesus is the tree of life.