Why was Kepler-22b an important extrasolar planet discovery?

Kepler-22b is considered a landmark discovery in the study of extrasolar planets because it was the first planet identified within the habitable zone of a star similar to the Sun.1

The habitable zone is the orbital region around a star where conditions may allow a planet to possess liquid water on its surface, a requirement essential to all known life on Earth. By detecting Kepler-22b, the Kepler mission provided a significant step toward its primary objective: determining the frequency of planets that exist in regions where life could potentially be supported. While the planet has a radius 2.4 times that of Earth, its location within this critical orbital distance made it a vital finding in the ongoing search for Earth-like environments in the galaxy.21