If you toggle it to off, you will only see the content posted to your local instance magazines. I’m on a smaller server and toggle it off from time to time to browse our All.

I’ve never had anything appear under the instance section yet.

I don't believe there is anything after that, it just has the status toggle. "On" will show you things from the greater fediverse (other kbins, lemmy, mastodon). "Off" will show you posts by users from your kbin, as well as replies from the fediverse on those posts that have been copied locally

(Edit: I just double checked and I'm pretty sure instances is just a placeholder for now)