In the world of alcoholic beverages, the bottleneck is the narrowest point of a bottle. It slows the flow of liquid. In the world of business and management, the bottleneck represents the narrowest point of a particular process. It slows the progress of development and thus constrains the whole process to its own limited capacities.
In manufacturing, the bottleneck can be a machine. In traffic, the bottleneck is a stalled car, an accident, or a construction zone. In the world of creativity and intellectual creation, the bottleneck is usually a person or a group of people.
Although potentially time-consuming and resource-intensive, upgrading a machine or clearing an accident is usually pretty straight-forward. Dealing with the human bottleneck isn't. Emotions make even broaching the subject tricky. Fixing the human bottleneck takes a lot more than just good project management - it takes a bit of friendliness, a good deal of empathy, and a touch of the Iron Fist approach.