How exactly does an Internet subnet work?

There are a couple of areas of computing that are guaranteed to make me tear at my hair with frustration, even after years and years of experience. One is configuring or customizing Microsoft Windows, which still baffles me at times, and the other is tweaking or configuring local area networks to have them optimally secure and efficient. That's why when I received a question about how to work with subnet masks, I was glad to call in colleague Chris Buechler for some expert advice. Between us we've created a pretty useful introduction to subnets:

    How does a subnet work?

Now if I could just figure out how to compare performance of the various PC chip families, all would be good in the world. :-)