Zettelkasten is a smart note taking system created by a German sociologist, whose productivity increased to epic proportions due to it1.

All notes in a Zettelkasten are linear, Atomic and autonomous#, with links created between them, enabling a Heterarchy# to evolve organically, rather than having to preconceive a hierarchy ahead (as is the case with outliners like Workflowy and Dynalist).