bottleneck is a phenomenon where the performance or capacity of an entire system is limited by a single or limited number of components or resources

Let us consider the following situation

We go to a washbasin and open the tap full. Now you will observe that water flows from the tap into the basin and it is drained by the sink hole . From the sinkhole it goes into the drainage pipe into the sewer. Now you block the ink hole and keep the tap full. You will observe that water is accumulated in the basin and the drainage pipe is empty. If you consider flow of water than it has the least flow rate at the sink hole (almost zero). Thus there is a bottleneck at the sinkhole.

Now let us take any industry. These industries have a lot of machines which have different operations. Now theoretically they should have same speed and operating capacity. With this, I mean that as soon as one process is finished another process should immediately begin.

However in practical this doesn’t happen. All machines are not manufactured by same company and also all models of the company do not have equal speed. Also the manpower operating the machines are not equally efficient.
Thus it results in unequal speeds and a process may not be started because of unavailability of raw materials. Also it will also happen that as another process is slow some raw materials will be accumulated before that junction.
Thus the junction at which process is the slowest , whose speed is equal to the entire speed of the operation is called bottheneck.

Now in order to identify the bottleneck, we need to observe the flow of goods and the machining process. The place where the raw materials have a tendency to get accumulated is known as bottleneck.

To remove the bottleneck we need to increase the speed of the process. We can do this by buying machines, increasing the number of machines or by bring more efficient operators for the process.