The historical format of the competition involves 12 teams, including the automatically qualifying host nation Japan, competing in the tournament phase for the title at venues within the host nation over a period of about two weeks.
The World Cup (with exception of the 2019 edition) acts as the first qualification event for the following year's Olympic Games with the top two teams qualifying.
Originally, each tournament had a different host, but in 1977 the competition was transferred to Japan on a permanent basis.
Instead of letting a consolidated event disappear for lack of interest, the FIVB decided to change its format in 1991: it would be held in the year preceding, and not following, the Olympic Games; and it would be considered a first international Olympic qualification tournament, granting the winner a direct berth in the games.
The possibility of securing an early berth for the Olympic Games, thus avoiding extraneous and in some cases tight continental qualification procedures, became a consistent motivation for the national federations to participate in the World Cup.
[1] The Women's World Cup has had not one great winner, like its counterpart for men's volleyball, but two: China and Cuba.
Then Cuba stepped forward to begin its amazing World Cup career, winning its first title in 1989.