What are Module Scripts what do they serve?

[RRandomkrys (Random)]

There are some great articles here about this subject. Here are a few:

When and how should I use ModuleScripts?

I’ve never really used ModuleScripts for anything other than using them to return text fields for GUIs. I would like to expand my usage for them. When and how should I utilize them, especially with large game projects?

_G or ModuleScripts?

I’m reorganizing a 10k line script I have into multiple scripts and ModuleScripts, it has a lot of _G functions and it gets quite laggy after a bit of time, would it be better if I replace the _G functions with ModuleScript functions? Would it cause any less/more lag or will it change nothing?

https://devforum.roblox.com/t/when-should-i-use--g-instead-of-a-modulescript/13444