Knoppix STD is a customized distribution of the Knoppix Live Linux CD.
Live Linux CD. Boot to the CD and you have Knoppix-STD. That would include a customized linux kernel (2.4.21 with ntfs rw, openmosix, and superfreeswan patches), Fluxbox windows manager, incredible hardware detection and hundreds of applications. Boot without the CD and you return to your original operating system. Aside from borrowing power, peripherals and some RAM, Knoppix-STD doesn't touch the host computer.
STD focuses on information security and network management tools. It is meant to be used by both the novice looking to learn more about information security and the security professional looking for another swiss army knife for their tool kit.