The Japanese translation for kanban is 'visual signal', in kanban projects, every backlog item is presented as a separate card on the board.
The main purpose of representing work as a card on the kanban board is to allow team members to track the progress of work through its workflow in a highly visual manner. Kanban cards feature critical information about that particular work item, giving the entire team full visibility into who is responsible for that item of work, a brief description of the job being done, how long that piece of work is estimated to take, and so on. Cards on virtual kanban boards will often also feature screenshots and other technical details that is valuable to the assignee. Allowing team members to see the state of every work item at any given point in time, as well as all of the associated details, ensures increased focus, full traceability, and fast identification of blockers and dependencies.