The basic idea is that you might start with a manual linkage between concepts, derived from linkages between content developed by subject matter experts, but over time it organically morphs into a knowledge graph that describes how certain concepts relate to and build on each other, and for which scenarios of learners.
That knowledge graph combined with a concrete goal (mastery level) and time to get there (deadline) can then be used to recommend to a specific learner what material to study or activities to do next.
It's theoretically possible to do this even more organically, but you need clearly tagged educational "stuff" (written content, lectures, activities, etc.) and, perhaps more importantly, clear ways to measure outcomes as a result of interacting with that "stuff" (typically quizzes which themselves have been clearly calibrated).
That knowledge graph combined with a concrete goal (mastery level) and time to get there (deadline) can then be used to recommend to a specific learner what material to study or activities to do next.
It's theoretically possible to do this even more organically, but you need clearly tagged educational "stuff" (written content, lectures, activities, etc.) and, perhaps more importantly, clear ways to measure outcomes as a result of interacting with that "stuff" (typically quizzes which themselves have been clearly calibrated).