Short answers, pulled from the story.
The 24-hour news cycle is the continuous, around-the-clock investigation and reporting of news, driven by fast-paced lifestyles and intense competition among media providers for audience and advertiser attention. A complete cycle includes both coverage of an event and subsequent coverage of public reactions to that coverage.
The 24-hour news cycle arrived with the launch of cable television channels dedicated entirely to news, which contrasted sharply with the slower day-by-day pace of printed daily newspapers. All-news radio had operated for decades before cable television, but cable brought a much faster pace of continuous updating.
Time magazine identified the O. J. Simpson murder case in 1995 as a significant early example of the 24-hour news cycle, noting this in 2015.
Online news sources, including blogs on the World Wide Web, considerably shortened the news cycle further after cable and satellite television had already accelerated it. Mobile apps added another layer of competition, with television, radio, print, and online providers all racing to deliver news first.
In their book Warp Speed: America in the Age of Mixed Media, Kovach and Rosenstiel wrote that "the press has moved toward sensationalism, entertainment, and opinion" as a result of the 24-hour news cycle. They argued the cycle encourages a "journalism of assertion" that prioritizes speed over whether a claim is actually valid.
According to Kovach and Rosenstiel, the 24-hour news cycle erodes the traditional values of verification, proportion, relevance, depth, and quality of interpretation. Corporate profit demands combined with intense audience competition push media organizations toward sensationalism and away from these standards.