In the Garden of Eden where god placed Adam & Eve, there was no death nor suffering, no sin nor no sadness. Complete trust of each other and god brought pure joy to every moment. God gave them everything they needed and it was a perfect relationship. They were free to do anything they wanted except eat the fruit from one special tree.
Satan basically told Adam & Eve that god was lying to them and that they shouldn't trust him. He also told them that god was bluffing about the punishment, which was DEATH.
Adam & Eve thought it over, trashed their trust over god, chose to trust the snake Satan and took a bite that would change the whole world.