To dumb down the idea of the hipster it is generally viewed as some one who follows the trend of not following the trend. I know it is a counter explanation but that counter kind of helps setup the expectations. What is "cool" to a hipster is what they in fact view as uncool its almost like taking the so bad its good approach towards fashion and with terrible results. That is my quick and dirty summary of how I see them. It does go beyond fashion but it is most evident by means of fashion choices.