What is a Kanban Board?
A kanban board visualizes workflow: columns for each state (to do → in progress → review → done), cards for work items, and WIP limits on the middle columns to stop starting and start finishing. The board makes the invisible visible — queues, bottlenecks, and the work nobody admits is stuck.
Board ≠ method: sticky notes in columns is a board; Kanban the method adds WIP limits, flow measurement (cycle time, CFD), and explicit policies. The limits are what turn a status display into a management system.
Worked example
A maintenance team's board shows "code review" limited to 3 cards. Thursday, a fourth wants in — the limit says no, so the developer reviews someone else's card to make room instead of starting new work. That tiny forced choice, repeated daily, is why their cycle time dropped 40% without a single process meeting.