For the uninitiated, it's called ANSI art. It's related, in a way, to a format you may be familiar with called ASCII art, which you see occasionally in emails.
ANSI utilized the extended dos (and amiga, but mostly dos) character set's solid, half, and dithered blocks, along with 16 colors (4 blues, no orange. wtf) on an 80 column screen. default rows were 25, but most ANSIs are "scrollers", that is they scroll off the bottom. Doesn't mean much anymore since you're likely seeing my work as thumbnails anyway.
ANSI got popular in the early 90s, with the rise of BBSes (this was juuuuuuust before the internet hit it big) accessed via dial-up modems. pushing high-res graphics through a 2400bps (or even 14,400bps) modem was crazy slow, so text graphics such as ANSI, which compress pretty well, were the order of the day. Artists were mostly grouped into art groups, who had an informal rivalry going on. The Artists would create works for BBSes, e-zines, friends, their own groups, and so on. Getting a piece done by one of the most highly sought-after artists was considered a very big deal, and often money changed hands for the most in-demand artists. To that end, the [RAiD] logo you see by my name in my art is purely a stylistic relic of the era. The "group" exists solely for my own interest in having a groupname next to my own name for legacy's sake.
ANSI is long past it's heydown now, with virtually no real "use" other than as pure art now. To that end, I find it a delightfully limiting medium. That's the point, to make something beautiful with very limited tools.
Don't bother looking me up, Cyonx did not exist during the heyday. I did plenty of art under another name, but none of it worthy of showing off. For comparison's sake, I would consider my own art to be upper tier, but hardly a master. Maybe a 6/10 or 7/10 compared to the best artists of the hey-day of ANSI art (circa mid 1995 from my point of view). Look up the work of Lord Jazz and Somms if you're curious.
Speaking of which, if you'd like to know more about the medium, or are even interested in making a piece or two of your own, strike up a conversation, I'd be more than happy to help you learn. start with sixteencolors.net for inspiration and grab an editor like pablodraw. Then make sure you let me know when you post something!
Edit 1-30-2013: Read Nootropic's commentary on ANSI's history and its peculiarities. He said it perfectly. fav.me/d4eu8p