A poser is essentially everybody in High School who actually pays attention to fashion/studies how to conform to a specific group. Generally, someone who is socially
awkward and/or physically unattractive gets called a poser when said individual tries to
fit into a certain group, usually comprised of
people who have been
studying how to conform for a longer period of time. However, since all High School cliques are based on extreme superficiality, the
word poser could apply to everyone in such a group. The idea that anyone is, in fact, a "
real" punk/
goth/hipster, etc, usually stems from how much dedication they have to putting together their personality. It's usually born from a psychological condition that has been impeded into their brain through corporate propaganda; more or less, the idea that you need to consume/conform on some level to have an identity at all.
When you are using external sources and symbols to define your personality, you are not actually being "
real" in any sense, and that's especially true if the symbols have been given their meaning independently of yourself or peers. Peer pressure and conformity, of course, are
normal adolescent behaviors, although teenagers take this to an extreme in consumerist societies (and corporations exploit this condition in teenagers as well, hence how important the
word "poser" seems to be here on
urbandictionary).
It should be noted, however, that some hipsters take this thought process
deep into their twenties, and never fully mature past the point of making an identity out of secondhand symbols or processes of thought (although this behavior has more complexity and nuance to it, and has more to do with boasting of education obtained at a university level, and classism). There are an enormous amount of college graduates in western
society with uniform tatse/clothing styles/mannerisms, with not only identical opinions, but identical expression of those opinions, and identical attitudes.
So, basically, "poser" is an Orwellian
word, that instills fear into the minds of teenagers (and some adults), which in turn makes them consume/conform in an efficient manner to avoid being labeled as such. For corporations, this is one of many tactics that help to create a very effective
society, where individuals place their own constraints instead of having those constraints come from a dictatorial system.