New to this so sorry if its a silly question,but what are the mods and how do they work???

The mods are in the creation and customization forum.

depends, you can mod the graphics, the game rules, the tech tree, the units.

A mod is a modification to the game in some way. You can use the Editor to alter it in all sorts of ways, with new graphics, new rules, new civs, new units, and so on. Have a look through the Mods and Scenarios sub-forums to see the sort of things you can do.

In other sites, I always see a mod, as a short term to moderators, so when I first come to the site, it was what I tough mod was.

I guess Plotinus get the title for both :p.

Yup, Woodelf and I are the modding mods. If only we also rode mopeds and wore long scarves. Well, perhaps Woodelf does, I don't know.