Short answers, pulled from the story.
The Antikythera mechanism is an ancient Greek hand-powered orrery, a model of the Solar System, and the oldest known analogue computer. It could predict the positions of the Sun and Moon and forecast eclipses decades in advance, and it could track the four year cycle of the ancient Olympic Games.
The Antikythera mechanism was retrieved from a shipwreck off the Greek island of Antikythera in 1901. It went unrecognized until 1902, when Greek politician Spyridon Stais noticed a gear embedded in one of the fragments.
No named individual is credited with building the Antikythera mechanism; it was constructed by Hellenistic scientists whose identities are unknown. Researchers have proposed links to Corinth, Rhodes, Pergamon, and the school of Archimedes, and the astronomer Hipparchus may have contributed to its lunar theory.
The Antikythera mechanism has been dated to between 205 BC and about 87 BC, with most estimates placing its construction in the late second or early first century BC. It must have been built before the shipwreck that carried it, dated to roughly 70-60 BC.
The Antikythera mechanism could track the positions of the Sun and Moon through the zodiac, predict solar and lunar eclipses years in advance, display the Moon's phase, and follow the four year cycle of Greek athletic games.
The Antikythera mechanism's fragments are kept at the National Archaeological Museum in Athens, along with reconstructions and replicas showing how it may have worked.