It's just note-taking in a single app, but instead of organizing your notes into folders, you link them. It's what Obsidian made popular. The name, because I use it for all facets of life, if I go to the doctor or dentist, I write it down, if I write an idea, or journal, it's all there. Tiago Forte coined the term initially. You find a note on my second brain about it, in case you want to know more (I also have related blog posts)
Nice, yeah, some call it a digital garden, some just a notes app. There are different views, hehe. Cool, would love to see what you're building, once it's ready.