I’ve only started looking into this, but my impression is that a Zettelkastan is both a thing (a big slip box of interconnected notes, either on paper or in digital form) and a methodology (literature notes, fleeting notes, etc). Something like Roam Research provides the slip box part, and you can therefore use it as a Zettelkastan, but the app also lets you use it as a personal wiki, possibly alongside the Zettelkastan functionality, if one wants to draw a distinction between the two. I’ve decided I want to try building up a Zettelkasten (I’ve settled on org-roam), but I think a personal wiki would be useful too, and I’m unclear if I should be keeping the two things apart.