The New York Times profiled how Korean online education sites have grown into some of the largest technology companies in South Korea:

About 2.8 million students, including approximately half of all college-bound high school seniors, are members of Megastudy, which allows them access to some of the country’s most celebrated exam tutors. For a fraction of what they would pay at traditional private “cram schools,” students can watch video-on-demand tutorials on home computers or download them into hand-held devices for viewing in the subway or parks. They can skip or fast-forward through some parts of a lecture and bookmark or repeat the rest.

Online education sites also got a boost when the Korean government announced plans to limit the operating hours of cram schools:

Market watchers point out that the Korea-specific phenomenon ― if the government tries to reduce private education costs in one area, the money will flow into another segment ― will offer a windfall to the country's education companies that have already chalked up fast growth over the past few years.