DORKS are the most 'mainstreamed' of this troika of dweebiness. Your dork is almost a normal human being; the quality of dorky is not strained. A dork is simply someone with an enthusiasm for something that, while not fully embraced by the popular culture, is also not entirely a "fringe" activity. In addition, your dork tends to enthusiastic about rather than obsessed by her pleasures; she is a fan rather than a fanatic. Dorks are, in short, people who are just slightly too fond of marginally acceptable activities. A dork is someone who likes Broadway musicals, legitimate theatre, Hummel or Precious Moments figurines, collectible thimbles, marching bands, or birdwatching. Your mother can be a dork, but not a nerd or a geek. Dorkiness is harmless, even cute; there is in dorkitude none of the malignance of the geek or the arrogance of the nerd. Dorks are our children, our parents, our cousins who collect coins. God smiles on the dork. (The teenage equivalent of the dork is the "fag", as in "band fag" or "drama fag"). If you have ever worn a 'Cats' sweatshirt, you are most likely a dork.
NERDS are perhaps the most misunderstood of the marginalia-enthusiast triumvirate. Simply put, the nerd is someone whose unpopular passion can be put to a practical -- indeed, even profitable -- use. If you make money, especially a lot of money, off of the activity that got you wedgies in high school, you are probably a nerd. The most common sort of nerd is the computer nerd, but there are nerds in all the sciences: physics nerds, chemistry nerds, engineering nerds, math nerds, even radio & telecommunications nerds. Indeed, nerdistry is almost a necessary component to a career in the science or technology fields. (The teenage nerd is a "wad", be he a gaywad, a dickwad or a dorkwad.) Since nerds have become more necessary to the smooth functioning of society in light of the increased role computers play in our lives, they have lost some of their outsider cachet; they have attempted to counter this trend by co-opting the term "geek". Make no mistake: an expert with computers is a nerd, not a geek. They may dress themselves up in the pejorative cool of geekdom, but computer nerds they were and computer nerds they remain. They will soon be the true masters of our society; they should revel in their nerdiness, not deny it. Nerds of the world, stand tall. Or as tall as you can, with your bad posture.
GEEKS are the bottom-feeders of the unholy trio of sit-at-the-back-of-the-cafeteria types. A geek may glory in his role (God knows I do), but secretly, he knows he is just playing semantic bingo. He knows that, like his chicken-decapitating namesake, he is the dregs of the dregs, the lowest of the low. The geek is typefied by his obsessive, fruitless dedication to and knowledge of phenomena of only marginal interest to even other geeks, and of no interest to normal human beings. Unlike the dork, the geek's passions lie not on the borders of popular culture, but in faraway lands of total lameness; unlike the nerd, his interests have absolutely no profit potential or practical value. (It is not for nothing that the teenage geek is known as the "loser".) The most common sorts of geek are comic book, science fiction, fantasy, role-playing and movie geeks; but there are as many sorts of geek as there are colors of the junk-culture rainbow. There are music geeks (and, even more stupefying, sub-genre geeks); there are romance novel geeks; there are sports geeks and internet geeks and real-vampire geeks. There is no theoretical limit to the sort of thing one can be geeky about, since there are a limitless number of inconsequential, pointless activities which normal people rightly have no interest in. I myself am geeky about things as commonplace as baseball and comic books, and things as obscure as postmodernism and underground rap music. Yet for all their flaws, the saddest thing about a geek is if he doesn't recognize who he is. A geek is a geek, but a self-denying geek is a geek's geek. Let your geek flags fly, my brothers, my sisters. Represent.