A Backlink is the link from one web page/note that lists another web pages/notes which refers to it. Within my Digital garden, backlinks are critical in making connections between ideas.
To be useful backlinks must be automatically generated.
Backlinks are important because content does not always flow in one direction and knowing what links to a particular page can create a more informative context or open up new avenues of learning.
Backlinks are not hierarchical and can end up creating circular references which is perfectly ok.