Kanban comes from a supply chain method developed in the 1940s by Sakichi Toyoda, the founder of Toyota Industries Corporation. It was invented as a Lean Manufacturing technique to optimize time, human resources, assets, and productivity, while improving the quality level of products and services.
Kanban does not have the same structure as Scrum. In a nutshell, there are no set schedules; no set releases or iterations; team roles are different; and the Kanban board itself is different. Kanban should be primarily used for projects in which requirements are unpredictable until the very last minute and/or release schedules are not of primary importance. Instead of limiting the work to be accomplished within a specific timeframe, like Scrum, limits are placed on the number of tasks being worked on at once. This is called a Work in Progress (WIP) limit. This methodology is often used for O&M contracts where production bugs or ad-hoc requests are common but cannot be predicted.
The Kanban approach allows for an issue to arrive without a set schedule and be handled by the team as it comes in. Kanban boards are typically used to move the work items through the lifecycle until completion. For more information on the Kanban approach, visit the Agile Alliance.