A punk is a term used to refer to a subculture of people who dress differently from ordinary conformist folk in order to show their individuality and/or offend mainstream people.
Punks wear any clothes which are not ordinarily seen on other people, but "typical" clothes of a punk includes; jeans (ripped, skinny, etc) or flannel trousers, baggy t-shirts, leather jackets, boots and short, sometimes coloured, spiked hair.
Originally started in New York City in the early 1970s, but really took off in London, England in the latter half of the 1970s with bands like The Sex Pistols. It became popular in America in the early 1980s with bands like the Dead Kennedys.
The punk movement was popular with a generation of lower-middle class men and women in their latter teens and early 20s. Many saw it as a way of rebelling against their upbringing and the general commercial direction which music of the 1950s, '60s and early '70s was taking. Accordingly, this rebellion against a stronger, conformist power gives punk the typical ideology of being liberal, or socialist. However, punks do not necessarily have to live by this, as there are conservative punks, as well as Nazi Punks.
Punk bands typically play hard, fast, aggressive songs, easy to play on guitars, drums and bass. Most songs are characterised by three or four Barre / Fifth chords played over and over again.
Example of punk bands include;
Note: Green Day is NOT a punk band.