I was unable to find any real explanation of what you can actually do with lua scripts elsewhere, so I guess I'll ask here:

How do they work with MP? Can you create a normal MP server/game/room which runs some particular lua script just like it runs a particular mod with particular settings? Or would the server be able to run only the mod, and each player would then have to manually run the correct lua script as well, or would even that not work?

Obviously you can do a lot of stuff with lua that you can't do with normal modding, so is there any way to create a mod+script combo that can be used in MP just as (or almost as) conveniently as a normal mod?