Refers to the center-west area of Japan, typically including Osaka, Kyoto, Kobe, and surrounding prefectures. Often contrasted with 関東地方 (Kanto region).
The Kansai region has major cities such as Osaka and Kyoto.
I'm going on a business trip to the Kansai region next month.
Refers to the Kanto region (Tokyo and surrounding prefectures), often contrasted with Kansai in terms of culture, dialect, and geography.
A more formal administrative term for roughly the same area as Kansai, though the exact prefectures included can differ slightly.
Compound of 関西 (Kansai, literally 'west of the barrier') and 地方 (region). The term historically referred to the area west of the Osaka checkpoint (逢坂関).