Come to UCSC and you'll understand. They are everywhere.
Basically hipsters are people whose defining characteristic is being unique. Their common stereotypical phrase is "I liked x before they were y" (the y generally being "cool" or "popular") This often also applies to clothing, where they strive to be bizarre or "ironic". Generally they wear extremely tight pants and some kind of ironic t-shirt (something extremely retro, things like that). They often sport some variation of eccentric facial hair, such as curled mustaches, handlebar mustaches, things like that. They best way to identify if someone is a hipster is to ask them if they are one; if they fervently deny it, they are surely a hipster.