distro is short for distribution. Sometimes users call it a flavor, a spin, a version.
The idea is central to how linux is different from Windows. Linux is free (as in “free beer”) and free (as in “freedom”). Basically what this means to the non-technical end user is you can do what you want with it.
Including repackaging/retooling/mutating/stripping the software and source code and making your own version called “Happy Holstein Linux”. And giving it to your friends. Or the world. Or selling it. Redistributing it. See? If you tried to do that with Windows you’d find yourself in a sharkpool of lawyers and/or prison.
Distros are intended by their creators to fill certain needs. If they were trucks some would be stripped-down fleet trucks. Some would be dualies. Gas vs. Diesel. 2wd and 4wd. Some are fully loaded Lincoln Blackwoods (shudder). Different tools for different jobs.
The job we address in this series is moving as painlessly as possible from Windows XP to Linux.