Faceted search lets a visitor narrow a result set by combining attribute filters such as price, size, colour, brand, rating or availability.
Also known as: filters, guided navigation
Facets work because they are reversible. Unlike reformulating a query, applying a filter is a low-risk, undoable move, which is why visitors who engage with facets convert at markedly higher rates than those who only re-type.
The quality of facets is a catalogue-data problem more than a search problem. Filters can only be as good as the attributes present on the records — and missing or inconsistent attributes are the usual reason a filter list looks thin or produces empty combinations.
Facets should be dynamic: only show values that exist in the current result set, show counts, and never let a visitor construct a combination that returns nothing without offering a way back.