Cha is the Japanese word for tea, and kombu is a type of seaweed. Real kombucha is seaweed tea and this video takes you to Japan's Rishiri Island, source of high quality kombu.
From Great Big Story:
Sorry to shatter the illusion, but that expensive, bottled kombucha iced tea you've been drinking isn't anything close to the authentic stuff—and, believe us, you're missing out. Come along as we travel to Japan's Rishiri Island and meet Chiharu Hirakawa, a shop owner and master of creating the real-deal drink. Located off the coast of Hokkaido, the remote island is famous for its locally-harvested kombu seaweed. Hirakawa uses the kombu, after it has been dried and powdered, to create traditional kombucha tea.