Translation Clarification on how to register my language in registry\locales.xml

I just need a confirmation.

I’ve been reading a lot of Translating Guideline but I am not yet to start translate it because I need to understand what I should be translating.

So this is just a simple question. I am using OJS 3.0.2 and I’ve been following instructions to start it.

In registry\locales.xml , the instructions said I need to declare my language first like this:

What I want to know is what does complete=“true” mean? does it mean that if the translation have been completed or not?

And the, iso639-2b=“eng” iso639-3=“eng”, what these both mean?

I just need a clarification. Sorry to waste any of your time since I am new at this.

P/s: I need to prepare the plugin for my language then I will give it to the admin of my organisation OJS…so what type of plugin it is? Is it some kind of file type or I just need to give him the OJS tar.gz file with my language added in it?