A bottleneck may refer to any of the following:
1. A bottleneck happens when too much data enters one source and causes a computer or network to slow down or become unresponsive. For example, a website could be mentioned on a popular page, which causes a bottleneck when their visitors all try visiting the page. In this bottleneck example, some visitors may encounter errors or unusually slow load times because too many people are trying to access the page at the same time.
A real-life good example of a network bottleneck was on September 11, 2001. On this day, terrorists coordinated four attacks across America. So many people were trying to visit online news sites at the same time to find out more about the attacks that most of the sites became unresponsive.
2. A bottleneck is also the weakest or slowest stage of a program or algorithm.