Pop culture (popular culture) is defined as youth culture that is loved by the mainstream. In Japan, pop culture tends to mean animation, games, and comics. Antonym for pop culture would be high culture which includes classic music, art, and something requires education in order to understand them.
Formerly, high culture used to be for only bourgeoisies or nobility who had a good education. For example, you needed knowledge of sonata form to enjoy classic music. Contrary to high culture, everybody could enjoy pop culture without education or particular knowledge. However, in 20th century, as the people have begun to have power, the definition of culture also changed. The number of the people with education increased, and then high culture gradually opened to the public. In addition, the development of mass media or technology of mass production made high culture more familiar to the people than before. We can see the famous paintings through the posters, and CDs, TVs, and radios provide us opportunities to listen music. High culture has assimilated to pop culture like.
The development of the Internet is also a key factor to connect the people with high culture, and also they create new pop culture. You Tube and ニコニコ動画 developed the concept of video sharing.