Punk is a term referring primarily to a youth subculture movement which emerged in the 1970s in New York City and London, England, although the term is used more loosely to denote many subsequent punk subcultures and subgenres. The original punk movement was a reaction to the commercial aspects of music and dissatisfaction with society as a whole, and as such it had a heavy focus on anarchism and rejection of authority.
 Origin of the term
Music critics had already applied the term "punk rock" as early as the middle 1960s to some garage rock bands, and applied it again in the early 1970s to Iggy and the Stooges and the New York Dolls. In this sense, "punk" was used as a slang term for inferior or amateur art, though Lester Bangs in particular applied it as a mark of approbation. When the Sex Pistols and the Ramones brought punk into its own as a distinct subculture and music style, the term stuck. However, a "punk" is also prison and street slang for somebody who is weaker who falls under the wing of a stronger person for protection, often a young homosexual who exchanges sexual favors for protection, and is also street slang for a young outlaw in general (as in "go ahead make my day punk"); it is possible the term was adopted with this meaning in mind as an anti-establishment statement.
 Aspects of the punk movement
 Clothing and fashion
Typical punks wore ripped jeans or plaid trousers with boots, leather jackets, loose fitting or tight t-shirts. The typical punk haircut is a mohawk, or mohican, in which hair at the sides of the head is completely shaved while the hair on top of the head was left alone, or hair was otherwise spiked up with gel and / or soap. Facial piercings were also a popular part of the punk movement, and one aspect of it which made getting through airport security very difficult for all parties involved.
One aspect of some of the more outrageous "costumes" was to enable disaffected British youths to remain on the dole, since no potential employer in their right mind would hire a creature so-attired.
It should be noted that punk fashion was and is not limited to any of these aspects of dress.
Punk music, in which the punk movement was rooted, was characterised by a drum kit, bass guitar, electric distorted guitar and vocalist, with fast paced songs and snarling, shouting lyrics speaking out against authority and other things of that nature. Songs typically consisted of a few chords being smashed out on guitar and were seldom longer than three minutes.
Original punk bands from the 1970s included Siouxsie and the Banshees, The Sex Pistols, The Ramones, The Clash, The Damned, and The Dead Kennedys, who experienced a mass underground following in the 1980s. Some music historians trace punk's origin to late 1960s/early 1970s bands from the New York and Detroit scenes such as the Velvet Underground, the New York Dolls, Iggy and the Stooges, and the MC5, although punk became a media sensation especially in the U.K. after the arrival of the Sex Pistols.
Early New York punk bands such as the Ramones did not tend to write political songs, although their angst-filled lyrics did explore controversial subjects such as solvent abuse, prostitution, Nazism and casual violence. It was the Sex Pistols who most firmly associated the punk scene (at least in the UK) with nihilism and anarchy, most famously in the songs "Anarchy in the UK" (1976) and "God Save the Queen" (1977). Additionally, The Clash became known for their left wing political songs, which were, arguably, more coherent and focused than the Pistols' more destructive anti-establishment anthems. Punk, like most other musical genres, began to embody a means of catharsis which could be used by anyone who wished to express themselves musically.
The nature of punk rock was such that it appealed to a very broad audience, whose political tendencies were not universally alike, thus punk ideology gradually became a cross section of the political spectrum, which does not exclude wingnuts. For example, the "Oi!" subculture (a working-class oriented punk movement) came to be associated with white nationalism. Over the years, there have also been a number of punk bands (e.g Skrewdriver, The Dentists and the Ventz) which explicitly promoted Nazi politics, hence the name "Nazi Punks". Despite the presence of racist punk bands, very few of the punk movement's defining bands were overtly racist. In fact, many of the defining bands of the 1970s punk scene in the UK (such as The Clash) had strong Reggae and Ska influences and close rapport with prominent Black artists, with whom they saw common cause. Moreover, fans of "Nazi Punk" bands are often looked down upon by other punks, as shown by the Dead Kennedys song "Nazi Punks Fuck Off" (1981).
 Selling out
The original punk movement was an outcry against rules, regulations, privilege and authority, and as such punk was originally an "underground" movement, in which bands played not for financial gain, but to register disgust with the established order. Punk bands that signed to major record companies rather than remaining independent or unsigned were regarded by many die-hard punk fans as "sell-outs". This has led to the claim today that the idea of punk and the punk movement is "dead", due to the lack of a strong underground punk movement reminiscent of the '70s. Some teenagers today can be seen sporting badges reading "Punk's Not Dead," on their shoulder bags, although die-hard punks would most likely disagree with this.
Some veteran punks (and numerous people you see commenting on YouTube videos of new age "punk" bands) from the original 1970s outfits reject the idea of punk today in bands that claim punk-ness but say and do everything which suggests otherwise. The best example today is the band Green Day, which gained mainstream popularity in 1994 with their album Dookie. After signing to a major record label, many original fans regarded them as sellouts, and after a new surge of popularity due to 2004's American Idiot, this view again came to light, particularly as they continued to claim to be "punk", despite expensive video shoots, tarting themselves up before shows with eyeliner, and the actual music digressing from original punk themes, leading to John Lydon (a/k/a Johnny Rotten) of the Sex Pistols and PiL calling them a "wank outfit".
 New Wave
Many bands emerged simultaneously with the arrival of early punk, sharing the punks' energy and DIY underground origins but not their nihilism or anger, and musically borrowing from a broad range of styles like glam, progressive rock, 1960s pop, funk, surf, and even disco and metal. At first the press lumped them in with punk but they soon got their own description, "new wave". Such artists included Talking Heads, Devo, John Otway, the Fabulous Poodles, Blondie, the Dickies, the Brains, Television, Elvis Costello, and the Boomtown Rats. Some early British punks, most notably The Clash and Gang of Four, expanded their repertoire in response and likewise became more new wave than punk. New wave became a catch-all term inclusive of everything from the most obscure punk to some rather commercial rock outfits like the Cars and Tom Petty, and all points in between. Eventually new wave became commercialized with the help of MTV to the point that it was more or less synonymous with early 1980s pop, in such groups as Duran Duran, Human League, Missing Persons, Men At Work, the Fixx and so on, to the chagrin of true punks. At that point, the term "new wave" fell out of favor as it was hardly "new" anymore, the less commercial new wave acts were re-framed as "alternative" and found a home on college radio, and punk once again arose as a separate scene re-affirming its anti-commercial roots.
 Hardcore punk
The demise of the original punk scene and the commercialization of new wave did not deter punk for long. In the early 1980s a new punk scene arose, trying to be louder, faster, angrier, and more nihilistic than the original punk scene. Labelled "hardcore punk" or simply "hardcore", these bands included Black Flag, Dead Kennedys, Fear, the Circle Jerks, Minor Threat, Bad Brains, Agnostic Front, etc. in the U.S., while the U.K. saw a new and explicitly leftist political punk scene in such bands as the Crass and the Exploited. Sub-subcultures arose within the hardcore scene, such as the anti-drug and anti-alcohol straight edge movement.
Hardcore is today usually remembered as simply "punk" rather than as a distinct "hardcore punk" scene. While the scene shunned commericalization, related genres emerged by the late 1980s, influenced by both hardcore and metal, which were openly commercial: thrash metal (Metallica, Megadeth) is one example. Grunge is another example, making a purported anti-commercial stance (along with angst and "slacker" posturing in general, in the form of "I suck, everything's my fault, I'm a creep, nobody cares, I'm so depressed" type lyrics) their commercial selling point, which pretty much made it impossible for any genuine punk expression after that point to be seen as anything but posturing. A few like Kurt Cobain couldn't handle the cognitive dissonance, the rest made a lot of money and paved the way for pop-punk bands like Green Day. See the "Selling out" section above. There was also a splitting of punk during the 1990s into various obscure micro-sub-genres along with the related arguments over how many bands can fit on the head of a pin, much as is also the case with heavy metal: metalcore, grindcore, vegan straight edge, riot grrrl, Celtic punk, noise, cowpunk, and dozens of others. A few of the more notable are detailed below.
 Street Punk
Modern hardcore has also merged with early Oi! influences to form what is known as "street punk." Street punk includes such bands as The Casualties, The Krum Bums, and Defiance. Street punks are sometimes dismissed as being "Fashion punks" by detractors for heavily emphasizing the "punk" looks of mohawks, spiked and studded jackets, etc. As a movement, however, street punk usually focuses on DIY and working-class causes.
Cyberpunk is generally considered a science fiction genre although some have embraced it as a lifestyle. Typically it focuses on the computer hacker (the malicious type) as the main protagonist/anti-hero. Often a hero will have several computers and monitors and will use their computer skills to break passwords, rob banks, or blow things up with a keystroke. For examples of cyberpunk read pretty much anything by William Gibson (whose Neuromancer basically codified the genre) or Philip K. Dick, or watch the Matrix. The basic point of Cyberpunk is the use of information technology in an attempt to subvert "the system." It also is heavily associated with techno music. Few real life crackers probably consider themselves cyberpunks. Some elements of cyberpunk can be seen and heard in the videos by the 1980's band Sigue Sigue Sputnik.
Steampunk is a sub-type of Cyberpunk, although instead of computers it relies on the use of Victorian technology. Typically they focus on anachronistic uses of technology, like analogue computer laptops or airships. Steampunks will often wear neo-Victorian clothing and combine it with modern punk aesthetics. Some will go so far as to build contraptions that actually work. Their calling card is a pair of brass goggles. Isambard Kingdom Brunel is not amused.
Based on the steampunk analogy, a few other genres have emerged. The first was arguably "gothic-punk", the name given by White Wolf Game Studios to the supernatural dystopian setting of their World of Darkness properties. Recent years have seen the addition of dieselpunk (something of an Indiana Jones aesthetic, based on the technology of the 20s through the 50s), and cowpunk (similar to steampunk, but a little further back and based on the American Old West).
A short-lived branch of 1980's punk rock was "Funnypunk", which mixed humor with the raucous music. Bands in this genre included Screeching Weasel and Adrenalin O.D.