When you see something like how you’ve shown, it’s basically declaring a variable as a certain type, example
local result : number = 10
This will say that the variable result is a variable for numbers. It’s mostly used for type checking when you have the script that has --!strict as the first line in the script, so the script wont complain at you about type errors
As for export, I’m not sure what are you talking about, could it have been a variable in the script?
The only place I’ve found something related to what you said was here, the Github page for luau. It’s at the very bottom, may that answers your question about exports?