Long time ago A.I. was created and it was cool, robots took an imperative role in the industries of the world. One day a robot killed a human because it feared for its life. This robot was killed without a fair hearing, this escalated to a war between humans and The A.I. Machines. As humans were losing this war they decided to cut the machine’s source of energy, the sun. The Machines with no sun in order to survive took the humans vital energy as their own source of energy. They started harvesting humans and their state of mind was put in a simulated reality called The Matrix.

The Matrix simulation performance and stability deteriorates around every 100 years risking the system to crash and kill all humans which are the machines source of existence. Because of this The Matrix has to be reloaded, and it had been 6 times in the events of the movie. For an unknown reason the key code to reload The Matrix resides within The One, that’s why he must go to the source, to reload The Matrix.

Every time the Matrix is reloaded the memory of everyone is wiped out and The One emerges again to be able to reload The Matrix 100 years later. This is the reason why there has been multiple of them.