Tree of Life and the Tree of Knowledge of Good and Evil.
Tree of Life and the Tree of Knowledge of Good and Evil are two specific trees in the story of the Garden of Eden.
Tree of Life served to maintain Adam’s biological processes for an extended earthly animal life. It did not provide immortality as such, for the tree, being finite, could not grant infinite life. Hence after a period of time, the man and woman would need to eat again from the tree or else be “transported to the spiritual life.” The common fruit trees of the garden were given to offset the effects of “loss of moisture”, while the Tree of Life was intended to offset the inefficiencies of the body.
Consuming the fruit of the Tree of Knowledge of Good and Evil was the original sin committed by Adam and Eve that subsequently became known as the Fall of man in Genesis 2-3. In Catholicism, the tree should be understood both symbolically and as a real tree - similarly to Jerusalem being both a real city and a figure of Heavenly Jerusalem. The fruits of that tree were not evil by themselves, because everything that God created was good. It was disobedience of Adam and Eve, who had been told by God not to eat of the tree, that was obnoxious and caused disorder in the Creation, thus humanity inherited sin and guilt from Adam and Eve’s sin.