Oringially zaibatsu were (yes, japanese) big Holdings, vertically organized and owned by a single clan, mostly started in the Meiji-Industrialization time. (1868-WW1 you could say)
They were uh... shattered (? the legal term) after WWII by the Allied Powers Command, since they were seen as key to the nationalistic (streamlined and often nationalized war) economy. Most of the names still live, like Mitsubishi, one of the original "big four".
After WWII they were "replaced" by the keiretsu, more informal, horizontally interconnected conglomerates (like holding a bigger amount of each others stock).
There are often similar but with a bank at the center. Again Mitsubishi is an example.
It is a interesting point of Japanese history in itself lol
Also one part of the explanation why Japans industry did so good. The parts worked together, often helping each other and because of the interconnection the pressure for short term profit was smaller, and long term strategic development weighted more.