Zettelkasten (from how I think of it) is a particular form of networked note-taking which lays out rough principles to follow in terms of how to create notes (nodes) and links (edges) within our note base.
At a high level, Zettelkasten provides guidelines on how to choose what kind of information becomes a unique note and what kind of information should contribute to existing notes. This is important because if done with care, the relationship between notes can add another dimension of value. It isn’t just the content of notes, but the relationships between them that can help generate insight and new ideas to think about.
This kind of writing can also have some neat effects on our own sense of self: zettelkasten spreads one’s mind across time.