Mod vs. Plugin on NMM, What's the difference?

[ARmodder]

I'll start off by saying I am very good at modding my games and making them stable, correct load order, cleaning the mod/making merged patches ect. But I never knew the difference between a Mod and a Plugin, other then a single mod may contain many plugins that add different features onto the core mod. My reason for posting this is simple in itself, less so when describing it.

I currently use several mods that are dependent to some extent on one another, Marts Mutant Mod, 20th Century Weapons- Reborn, CALIBR, CRAFT, and FO3 Wanderers Edition and one non related mod Feng Shui, well Feng Shui requires use of NumEnter and will not work if any other mod installed uses it, for me this was FO3 Wanderers Edition. Now not wanting to trade one for the other, I started un-checking all the FO3 Wanderer Plug-ins but keeping the mod itself active, then I launched my game via FOSE thinking it would CTD on launch, it didn't and what's more is not only did both FO3 Wanderers Edition work but so did Feng Shui, so I'm very happy of course, now I decide to activate all but the FO3 Wanderers Edition.ESM Plug-ins thinking "this will be the one to break it" and again it worked perfectly, so my question is how did the plugins or the mod for that matter work with the plug-in ESM file not activated?

I am just curious as it took me about an hour and a half of editing values in FO3Edit for keybindings, and doing over 20 test runs, and mod/plug-in activating/deactivation to get it to work, also for those who want a ton of good mods the aforementioned mods are epic, 20th Century Weapons-reborn, adds 152+ weapons with over 900 variants! and FO3 Wanderers Edition has Primary Needs (eating, sleeping, drinking) as well as over 20 features that add items and difficulty to the game, as well as grenade hotkeys for throwing, and a door breaching interface!

[Incunabulum]

A mod is all the plugins required to make the mod work.

All plugins are mods

Plugins contain the data/changes that the mod does.

Keep in mind, for mods that change the same things - the lower plugins on the list will overwrite the changes made by the higher.

So if you have two mods that make changes to the same entry (but otherwise do different things elsewhere) you will have to decide which one 'wins' by placing it below the other. And doing so can (not will, *can*) break other mods that are dependent on the loser as.