Information Architecture

Information architecture is the structural design of shared information: how it is grouped, what things are called, how navigation works, and how search behaves. It is distinct from visual design and from content, and it is usually the thing people mean when they say a site is confusing.

Its core activities are organisation (how items group), labelling (what those groups are called), navigation (how people move), and search (how people find directly). Labelling is the hardest and most consequential — a category named in the organisation's vocabulary rather than the audience's is invisible to the people it was built for. See Naming and Plain Language.

Two ideas do a lot of work. Findability is the property that a person can get to a thing; understandability is the property that they know what it is when they arrive. A structure can have one without the other.

At scale the interesting problems become taxonomic: whether structure should be a hierarchy, a set of facets, or a graph of relationships. Content systems that model structural role separately from subject matter can recombine the same material for different audiences, which is exactly the modelling that a fixed hierarchy prevents. See Taxonomy and Knowledge Graph.