To conform means to fit into something, to mold into the shape of another vessel or into a shape that another entity wants you to be in. Conforming is modifying something to be something else, something that it may not actually be.
In the United States great value is placed in being able to conform, despite our ostensible love of freedom and individuality. Those are fine, as long as you fit within the container of mainstream society. There really isn't a real desire by the bulk of society to see people who refuse to fit within it.
We all conform to be part of groups of people. Especially groups of people we like, for whatever reason. We usually aren't completely like other people, so we conform our external appearance and actions to mesh better with them. Sometimes, we actually change and become more like them; other times, we remain superficial.
Even if you fight conformity you're conforming with those who choose to fight conformity (please see bad paraphasing of Rush lyrics for a better explanation.)