-when, where, and who created this system?
-what was it about?
-why was it important?
Toyotomi Hideyoshi and Tokugawa Ieyasu both get credit for creating the system, although it saw its greatest use during the Tokugawa shogunate which officially began in 1603. It was a system in which the daimyos, provincial feudal lords, had to spend alternate years in Edo, the capitol, away from their home provinces. When they were not in Edo, their wives and heirs were kept in the capitol as hostages.
This system was intended to weaken the daimyos by forcing them to be constantly on the move and forcing them to spend large sums in order to maintain multiple households and constant processions. This system was important because it arguably led to much development of transportation infrastructure in Japan and because it kept the daimyo weak and unable to rebel against the shogun.