Knoppix is an operating system based on Debian designed to be run directly from a CD / DVD (Live CD) or a USB flash drive (Live USB), one of the first of its kind for any operating system. Knoppix was developed by Linux consultant Klaus Knopper. When starting a program, it is loaded from the removable medium and decompressed into a RAM drive. The decompression is transparent and on-the-fly.
Although Knoppix is primarily designed to be used as a Live CD, it can also be installed on a hard disk like a typical operating system. Computers that support booting from USB devices can load Knoppix from a live USB flash drive or memory card.
There are two main editions of Knoppix: the traditional Compact Disc (700 megabytes) edition and the DVD (4.7 gigabytes) "Maxi" edition. Each of these main editions have two language-specific editions: English and German.
Your purchase will be for the "Maxi" edition, which is the most complete and comes packaged with an extensive array of awesome software.