In the Book of Genesis, the tree of the knowledge of good and evil or
the tree of knowledge (occasionally, the tree of conscience,) was a tree
in the middle of the Garden of Eden. (Genesis 2:9).
God directly forbade Adam (Eve having not yet been created) to eat the
fruit of this tree.
A companion tree, the Tree of Life, was in the garden, also.
A serpent tempted Eve, who was aware of the prohibition, to eat the
forbidden fruit from the tree of the knowledge of good and evil (Genesis
3:1-6).
The serpent had suggested to Eve that eating the fruit would make one
wise.
Eve and then Adam ate the forbidden fruit, and they became aware of
their nakedness (Genesis 3:6-7).
After discovering their disobedience, God banished the couple from the
garden in order to deny them access to the Tree of Life which would give
them immortality.
God cursed both the snake and the ground, obliging Adam to survive
through agriculture "by the sweat of his brow." He told the woman that
her childbirth pains would be greatly increased and that the man would
rule over her.
God set a guard about the garden to protect the tree of life from Adam,
Eve, and their descendants. (Genesis 3:14-24)