Zettlekasten is a method of storing information invented by Conrad Gessner.
In Zettlekasten you are supposed to create little cards and then file them. I don't really know how Zettlekasten are supposed to be used. I think I'm somewhere between a Zettlekasten and a wiki.
For a long time I used Obsidian to manage a knowledge base.
Org-roam is a method of building zettlekasten or personal knowledge bases in Emacs Written by Jethro Kuan.
Here is a link as to how Jethro uses Org-roam : https://jethrokuan.github.io/org-roam-guide/