Why are subcultures seen as a subculture?

To have a subculture, you first need to have a culture. A culture is usually noted as a group with the same beliefs, ideas, goals and much more. It can be seen as being the summation of ways of living, by a group of people and can be passed down through generations. No one ever agrees on everything, and eventually things come to a point where those who are not happy with some of the norms or beliefs of the rest of the group, will splinter off and become a group of their own. While many of the beliefs that they hold are still those of the original culture, they do have major differences of opinion on one or more issues. The group that has chosen to leave, although they have much in common, is now a subculture of the original culture. You could say that they are of that culture, but a little different.