Kanban is a signaling system to trigger an action; historically and as its name would suggest the system was demonstrated with a set of cards.

It was out of a need to maintain the level of improvements that the Kanban system was devised by Toyota. Kanban became an effective tool to support the running of the production system as a whole and in addition, it proved to be an excellent way for promoting improvements because reducing the number of Kanban in circulation highlighted problem areas.