Faceted navigation may be the most significant search innovation of the past decade. It features an integrated, incremental search and browse experience that lets users begin with a classic keyword search and then scan a list of results. It also serves up a custom map that provides insights into the content and its organization and offers a variety of useful next steps. In keeping with the principles of progressive disclosure and incremental construction, it lets users formulate the equivalent of a sophisticated Boolean query by taking a series of small, simple steps. Learn how it works, why it has become ubiquitous in e-commerce, and why it’s not for every site.