A bottleneck is the term used for any function, department, resource or facility whose needed capacity is less than the demand being placed upon it.
If we were to fill an entire bottle with marbles and then try to dump them out the marbles would bottleneck just as shown in the photo above. This is because the neck is much narrower (needed capacity) than the demand (marbles) being placed upon it.
A great book written by the creator of the Theory of Constraints for removing bottlenecks is The Goal: A process of Ongoing Improvement.
Subscribe below and receive lean, six sigma, operations, supply chain, logistics, distribution and business terms in your mailbox.