This information will, of necessity, be incomplete and out-of-date as soon as it is posted. This is because no official body has sat down to actually define the terms I will attempt to explain and also because the general usage of many of the terms has evolved and changed since Linux was first introduced.
At one time, when you selected a Linux distribution, you knew pretty much what you were getting. Today, most linux distributions offer so many choices and options that you cannot be sure what the finished product will look like nor how it will behave. This article will try to define for you what these choices are. No so much the actual choices, but what the words you will encounter when trying to decide refer to.
One of the main functions of a Linux "distribution", as the name implies, is to distibute software to you, and your choice of distribution determines how you will need to do this. The most ubiquitous way of distributing software is that of the GNU Debian distribution, which uses software, both command-line and GUI, based upon the apt command. Ubuntu and its many variants use this system as well. Two other widely used systems are that of Fedora, which packages its software in rpm files that are removed and installed using the dnf command, and that af he Arch distribution and its many derivatives that use pacman as a package manager. Additionally there are quite a few other package management systems, less popular, but perhaps equally efficient, that I am not familiar with.