A beginner's guide to mods?

[David G]

Considering the years I have spent playing this game, it must be about time for me to find out what mods are and how to use them.

There is a helpful file called "Read_Me_First.txt" (kind of a clue!) in the User_mods folder, but this leaves some questions unanswered (and also says it is last updated in 2011 but refers to JTCS 2.0. (?))

My questions:

(i) I think "mod" stands for "modification" - correct?
(ii) Do the mods only affect graphics or also rules? Or does it vary depending on the mod?
(iii) Assuming it's just graphics, can one player be modded and the other un-modded and still play?
(iv) Have I missed a help resource about this?

Thanks,

David