A subculture is a cultural subgroup. They are considered 'opposite from the mainstream culture because of their unique trends. Subcultures are judged by what they look like, what they wear, where they live, their ethnic background and religion. Subcultures have distinctive styles of dress, activity and music. They form when the main stream culture fails to meet the needs of a particular group of people.
Let's take a look at a known subculture. A perfect example is the punk subculture. Here is how they are perceived:
Punks are young (16+), and known for being rebellious. This started during the 1970s in Britain, where a group of young rebellious teens decided to make a point through music, clothing, and violence (Rebelling against the government). They don't like to dress appropriately because it is a way they express their hatred to the mainstream culture. They wear clothes such as worn out or ragged jeans, black and daggy t-shirts, with offensive words written on them.
They have unusual wildly spiked coloured haircuts, and body piercing. Punks believe in excluding themselves from society by being different (odd or rude clothing). This is a sign of rebel, a big bald sign with the words "THIS IS HOW WE EXPRESS OUR ANGER TO YOU". Music plays a big factor in the punk subculture. There are also punk bands which fills teens with negative thoughts. For example, Marilyn Mansons music is well known as Punk. His songs focus on sex, drugs, pain, and most influentially rebelling against parents.
Ultimately, Punks are universally different from the mainstream culture. Mainstream cultures wouldn't listen to Marilyn Manson, My Chemical Romance, Slayer, or Pantera. Instead, they'd listen to Hilary Duff, Britney Spears, Yellowcard, James Blunt, or David Gray. The entire lifestyle of punk is made into a culture of its own e.g. the people, fashion, and through the music.