While it’s reasonably well known that Gaia and Uranus were the parents of the gods, and in particular, the Titans, what most don’t remember is that they sired many other children as well, including many monstrous things.
Uranus will never be accused of being father of the year, though some gods were much worse. In this case, he is so horrified by his own children that he banishes them to Tartarus. Tartarus is the underworld, essentially Hell. It is the same place the Titans will be banished to after they lose their war with the Olympians an age later.
This act will ultimately lead to the downfall of Uranus, Chronus and the Titans as a whole.