The Bible makes it real clear in Genesis chapter 2 and chapter 3
That God created Adam, the first man
Then out of Adam, He made Eve
And God and man in a perfect relationship
No problems, no pain, no suffering
No beef, you know what I'm saying?
But God told Adam not to eat from the tree of the knowledge of good and evil
Coz He said the day that Adam does that, he was surely gonna die
But the serpent was the most cunning creature of them all
And he deceived Eve into eating from that tree
And then Eve gave to her husband Adam
And that's when sin entered into the world
And Adam represented all of us, all of humanity
Past, present and future
And we fell short of God's standard, perfection
That's why we call it the Fall of Man
And that's why our world is fallen