I've heard people reference this platform before, but I have no idea what it is. I just looked at the substack.com, and I feel like I still don't understand it.

Is it a blogging platform mixed with a newsletter tool?

Either I missed it entirely, or the landing page assumes I know what it is before I get there.

Even the about page is buried in "link soup" at the bottom of the page and just leads to hand waving and eventually a short story about something in 1833.

I don't know what needs to be built, but I do know that I don't know what this is.