Jeff has a pretty interesting explanation of what the site is all about:
Stackoverflow is sort of like the anti-experts-exchange (minus the nausea-inducing sleaze and quasi-legal search engine gaming) meets wikipedia meets programming reddit. It is by programmers, for programmers, with the ultimate intent of collectively increasing the sum total of good programming knowledge in the world. No matter what programming language you use, or what operating system you call home. Better programming is our goal.
Having been part of the limited private beta for a few weeks and now the public beta, I can honestly say the way Stackoverflow works is truly unique and rather effective.
Be sure to check it out and start earning your reputation points.