As you move along your journey, whatever it is, you’ll find an obstacle. In productivity terms, that’s a “bottleneck”, and it is exactly that: a narrowing of your throughput at that point. Just like at the neck of the bottle, where the liquid cannot rush out faster than the mouth of the bottle would allow it to, a bottleneck in work or life, or any process; holds back throughput.
One important thing to understand, is that while it is usually found at a specific point, the bottleneck affects the whole system. No other part of the system, no other people, can go faster than what the bottleneck dictates. This is how we get cars that cannot be produced because of missing chips, or why we can’t deliver vaccines faster, because of lack of -80 C fridges.
But a second thing to recognize is that finding a bottleneck is not the same thing as finding the root cause of having a limitation. They can or can not be the same. More often than not, they are not. And then, you will make some progress, until you find yet another bottleneck.
The only thing that the bottleneck can guarantee, is that spending some resources in eliminating it, will be the fastest way to make some progress.