"The mainstream comes to you, but you have to go to the underground."
- Frank Zappa
Underground culture, or just underground, is a term to describe various alternative cultures which either consider themselves different to the mainstream of society and culture, or are considered so by others. The word underground is used because there is a history of resistance movements under harsh regimes where the term underground was employed to refer to the necessary secrecy of the resisters.
For example, the Underground Railroad was a network of clandestine routes by which African slaves in the 19th century United States attempted to escape to freedom.
The unmodified term "The underground" was a common name for World War II resistance movements. It was later applied to counter-cultural movement(s) many of which sprang up during the 1960s.
These 1960s and 1970s underground cultural movements had some connections to the "beat generation" which had, in turn, been inspired by the philosophers, artists and poets of the Paris Existentialist movement which gathered around Jean-Paul Sartre and Albert Camus in the years after World War II.
It took a few years more, however, for the culture Kerouac describes to grow in numbers and redefine itself variously as the underground culture or the freak scene etc.
Since then, the term has come to designate various subcultures such as mod culture, hippie culture, punk rock culture, techno music/rave culture and underground hip hop.
Applied to the arts, the term underground typically means artists that are not corporately sponsored and generally do not want to be. However, with the advent of the world wide web (or internet), many experts argue that there is no underground since so much art and so many political ideas, especially music, is far easier to locate and because so it provides artists and activists a means to promote their work and ideas without large, established corporate interests. Even the concept of obscurity is questionable given 21st century access to information about past or current artistic trends.
The Ben Folds Five song "Underground" pays homage to alternative culture.
(Source)