The Dot-com crash began after the bursting of a technology-stock bubble centered on internet companies.
The Nasdaq Composite reached a peak of 5,048.62 on March 10, 2000. Many internet businesses had attracted enormous valuations despite limited revenue, large losses, or untested business models. When expectations changed, technology shares fell rapidly.
The Nasdaq lost about 78% of its value from its 2000 peak to its October 2002 low. Numerous dot-com companies failed, while established technology firms also suffered severe declines. The downturn contributed to a U.S. recession in 2001, though the crash was one part of a wider economic story.
The phrase refers to the market collapse, while the Dot-com bubble describes the preceding period of speculation. Not every internet company disappeared: Amazon and eBay survived and later became much larger businesses.