A WIP (work in progress) limit is a strategy for preventing bottlenecks in software development.
Work in progress limits are agreed upon by the development team before a project begins and are enforced by the team's facilitator. For example, a team may divide the tasks that must be performed for a feature into design, code, test and deploy. When a WIP limit for a certain task has been reached, the team stops and works together to clear the bottleneck. The goal of working in this manner is meant to ensure that the entire team takes ownership of the project and produces high quality code.
WIP limits are often visualized with Kanban cards. The cards, which are often just post-it notes, represent work in progress. To visualize work flow, Kanban cards are posted on a board in queues representing the status of the work. The queues in the example above would be labeled "design," "code," test," and "deploy." A Kanban board makes it easy for the team members to visualize the point at which a WIP limit has been reached because the queue will have an unacceptable number of Kanban cards in it.