How mods work in the Witcher 3 - basic concepts for dummies (the Witcher 3: Wild Hunt)

Since the forum is constantly updated with all sorts of messages "the game with mods does not start!", "Mods do not work!" and so on and so forth.
I want to briefly explain how the game interacts with mods.
So: everything that is in the mods folder and has "mod ..." in the name, the loader loads first of all, using the alphabetical order in the names of the mod folders to set the priority, after, of course, these "mod .."
Mod files replace similar files of the original game (sometimes there are own mod files, but they are written into the logic of the game in the mod files mentioned earlier). That is, if some say "modA" replaces some blaby file from the game, then if another mod "modB" also uses this blaby file, then its version of this file will no longer be used in the game. And therefore, in the script versions of the mods, errors occur during compilation, since some other files of the "modB" mod are loaded, but refer to the functions that were written in the blablab file version in the "modB" mod, but since it was priority the blabble file from the mod "modA" is used, not even from the game (!!) then these functions are not there, which causes errors.
In general, the summary - the files of the game are used only one, from the game, or - from some kind of mod! If several mods use the same file, only one will be selected for compilation. And, yes, if this selected file does not correspond to some of its data with the game files (for example, a file from the old version of the game is used in the mod), then, of course, the game will not work normally or use this file (mod), since the file completely replaces the original file from the game!
I hope that I tried to explain more or less clearly how it all works =)

Tips - if several mods use the same files, you need to combine all variants of this file into one version. You can do this manually, but it is better to use the Witcher Script Merger program, which in a semi-automatic mode creates a combined version of the disputed files, and places it in the "mod0000" folder, which receives the highest priority (four zeros in the name), and all files into the game loaded from it. Also, the program simply scans all mods at startup and displays their conflicts.