A structured network of entities (people, concepts, products) and the typed relationships between them. Unlike a folder hierarchy or a flat tag list, a knowledge graph captures meaning through connections — "Tobi Lütke cites Inner Game of Tennis," "Rippling attacks Workday" — and lets you traverse ideas the way you actually think about them. The core concept behind the Personal Knowledge Graphs book and the reason Obsidian works: every wikilink is an edge.