What is the difference between a mod and an add-on?

[RL Clown]

I know that I sound like a noob when I ask this type of question, but seriously, what is the difference between a mod and an add-on? This topic has puzzled me for several months...

[Syluxguy28O3]

a mod changes the main game, while an add-on adds content to the main game.

[talisa]

if you are talking about quake:

MOD:
with mod people mean modified QC, a progs.dat which changes anything about gameplay.
like for example quoth or drake are examples of mods,

or if a map comes with its own progs.dat cuz something was changed about the gameplay,
like new or modified monsters or weapon-changes or such the progs.dat that changes the gameplay is the 'mod'

.

ADD-ON:
in quake people generally people refer to items like replacement models as 'add-ons'. they dont actually change gameplay,
but are merely meant to enhance the looks of the game without changing anything about how the game plays.

perfect example of what people refer to as add-ons are HD models and textures,
which are made to make the game look more pretty but dont change anything beyond looks

[Spirit]

There are no conventions.

[MadGypsy]

Mod is short for modification so, a mod would be anything that exacts a change on an existing element or function. An add-on would introduce some element or function to the game that does not currently exist. However, both of these terms imply the other so, there is no difference between a mod and an add-on. To mod is to add and to add is to mod. The only exception I see is if you were to mod in a way that removes elements or functions without supplying a replacement. In which case you could not call your changes an add-on.

[Pvt. Gerpsnot]

Mod is short for modification so, a mod would be anything that exacts a change on an existing element or function. An add-on would introduce some element or function to the game that does not currently exist.

And all this time I thought "Zeus" was a mod :-p