A bottleneck is a situation or location in which progress stops or slows significantly. In production, a bottleneck could be a machine or facility that limits the overall output of a system or company, and the term expands in Critical Chain to encompass processes that are needed across multiple projects or steps within a project. For example, Genemodem’s digital processing department is a bottleneck because all projects have at least one step that needs to be put through this department, leading to a significant slowdown of progress at those steps.

A buffer is anything that puts distance or protection between two potentially conflicting elements, such as a jacket providing a buffer against cold weather. In Critical Chain, buffers are used in production to protect a system from breakdowns, bottlenecks, and inventory issues, such as allowing a buffer of resources to build in front of a bottleneck process to ensure continuous operation of the bottleneck. Richard’s class discovers that buffers can be used in project management to protect specific steps and tasks, as well as the critical path, itself, by using buffers of time to protect against delays.