One of the two named trees in the Garden of Eden. This tree apparently allowed those who ate from it to live forever.
After the first couple (Adam and Eve), ate fruit from the Tree of the Knowledge of Good and Evil, God barred them from the Tree of Life. In fact, he banished them from the garden, setting cherubim angels and a flaming sword at the garden entrance to guard the Tree of Life.
Much later, after all other events in the Bible, the Tree of Life is seen again, though this time it’s in the midst of a garden city, the New Jerusalem. In the city, apparently all believers will be able to eat of its fruit. Additionally, the tree’s leaves will be used “for the healing of the nations”.