It's called 'shared' and if you type it into script editor you will see it shows up as a built-in function and Roblox doesn't provide any documentation on it. Does anyone know what it is/what it does?
If you open a script and simply type in "shared" it will show up.

1 comment
sharedis not a function. It is a table. It works exactly like_G, but don't use it either, use module scripts instead if you want global variables.