The sin that was committed in the Garden of Eden by Adam and Eve. Eve picked of the fruit of the tree of knowledge and evil and ate of it with her husband, Adam. Forget all the lies that the Catholic Church teaches, baptism by water from a priest to a baby does not, I repeat DOES NOT!!! get rid of original sin, if this were the case, humans afterwards would not be born with this stain and then we would be sinless. Only cure for this is the atonement of our Lord and Savior, Jesus Christ of Nazareth. Being a changed (born-again) person and at physical death, if we have truly believed in his redeeming power over us and learned to forgive everyone, as Jesus did, will we be free of this stain and enter into the kingdom of our Heavenly Father, YAHWEH.
Original sin is what caused Adam and Eve to through away Paradise in their physical life, this caused them to be cursed more than the animals by the LORD, YAHWEH. This also causes all the other sins in the world and it has caused alot of evil in our world.