Deb files or Debian Packages
What is a .deb file?
In the Debian Linux distribution (on which Knoppix is based), software is commonly distributed in the form of Debian packages with the .deb file extension. A Debian package is a single file archive which contains the files related to installing a particular program. Also included in the Debian package is a control file which lists what additional Debian packages need to be installed in order to get the program to run. These additional packages are commonly also .deb and are called "dependencies". For more information on the Debian package management system please see: Deb file format.
Because Knoppix is based on Linux, it is possible to download and use .deb files as in order to install new programs into Knoppix.
What you should beware of
Installing a .deb package
Using the GUI
Using the Command-line
Please see here: dpkg for information on how to use the dpkg command at the command-line.