What is the Core packages folder?

So I’ve seen this folder be in studio time to time, sometimes its there and sometimes its not. And whenever I click on it, it says I lack permission or something like that. Is this a studio bug?
core

what2
I’ve seen this for a long time now and I have no idea what it does.

The documentation says a little about what they are.

CorePackages

There’s might be more info you can find, but using Google can probably help you.

I’ll probably get falsely flagged if I post a google link.