1. In Greek mythology, the twelve titans were the children of Uranus / Ouranos (heaven) and Gaia (Earth). One of them, the youngest, was Chronos (time), who became supreme ruler of Heaven and Earth, by castrating his father, and killing most of the other Titans.
Later on, Chronos would be defeated by his youngest son, Zeus.
2. As a symbol, titans represent the forces of manifestation.