Zettelkasten
A Zettelkasten (German: ‘slipbox’, plural Zettelkästen) or card file consists of small items of information stored on Zetteln (German: ‘slips’), paper slips or cards, that may be linked to each other through subject headings or other metadata such as numbers and tags. It has often been used as a system of note-taking and personal knowledge management for research, study, and writing.
This is the basis for org-roam.