What are reverse indexes?

A reverse index is a data structure used primarily in search engines. It functions similarly to an index in the back of a book, where terms are listed along with the pages they appear on. In the context of digital documents, a reverse index lists terms and links them to the IDs of the documents where those terms occur, detailing the specific location within the documents and the context in which they appear. This structure allows for efficient searching because it directly connects search terms to the documents containing them, without having to scan all text data 1.