It looks awesome, thanks!

Bad thing is that the website has almost nothing on it. I don't know if it's a service, a downloadable app, a self-hosted web app, or anything.

And the text on the website is light grey on a white background so it's very difficult to read.

I found more information on the github, but it still needs screenshots and information on how to actually use it (download? self-host on server?)

https://github.com/oschettler/knowfox

So I discovered that Knowfox can be used on the main website by registering an account there.

I did so. One thing that is noted is that everything is private by default. What does that actually mean? Even on the github, I couldn't find any kind of description of what "private" means? Is it e2e encrypted? The keys are saved somewhere on my device?

When I create a new concept, I see it has a relations config at the bottom of the concept creation page. How do I use the relations that I define there?