Short answers, pulled from the story.
Cronus was the leader of the Titans and the youngest child of Gaia and Uranus. He overthrew his father by castrating him with a stone sickle, then ruled the cosmos alongside his sister Rhea during the mythological Golden Age, before being overthrown in turn by his son Zeus.
Cronus swallowed his children because Gaia and Uranus prophesied that he would be overthrown by one of his own offspring, just as he had overthrown his own father. He devoured Demeter, Hestia, Hera, Hades, and Poseidon as each was born to prevent the prophecy from being fulfilled.
Rhea, advised by Gaia, gave birth to Zeus secretly in a cave on Mount Ida in Crete, then wrapped a stone in swaddling clothes and presented it to Cronus, who swallowed it believing it was his infant son. Zeus was hidden and raised in Crete, guarded by armored dancers called Curetes who clanged their shields to mask the baby's cries.
Most sources, including the Iliad, Hesiod's Theogony, and Apollodorus, say Cronus was imprisoned in Tartarus after the Titanomachy. However, two papyrus versions of Hesiod's Works and Days and the poet Pindar, in a poem from 476 BC, describe Zeus eventually releasing Cronus so that he could rule over the heroes in the Isle of the Blessed.
The Romans identified Cronus with their indigenous deity Saturn, celebrating him through the Saturnalia festival and building him a temple in the archaic Roman Kingdom. This connection gave rise to the English word Saturday, derived from the Latin Dies Saturni, and to the naming of the planet Saturn, the outermost of the classical naked-eye planets.
Ancient writers frequently linked Cronus with the personification of time, Chronos. The philosopher Cicero in the 1st century BC argued the two names were synonymous, since Cronus governed the cycles of seasons. Plato in his Cratylus noted the connection, and the Neoplatonist Proclus in the 5th century called Cronus equivalent to the originating cause of all things.