Open source desktop basics: Risk-free ways to get started, part 2 has an intro to Knoppix and LiveCDs aimed at the business PC user. The article explains what a LiveCD is and what it can do in an accurate and understandable way.

It’s easy to take Linux for a test drive. Some Linux versions have been tailored to run from a CD. You just put the CD into the drive, reboot your machine, and Linux will be up and running. No installation is required; nothing will have to be written to your hard disk. When you’re done, take out the CD and reboot your PC again, and you’re back in Windows.