Stands for "Wide Area Information Server."
WAIS (pronounced "ways") was a client-server database search system introduced in 1990 before the widespread adoption of the World Wide Web. It indexed the contents of databases located on multiple servers and made them searchable over networks, including the Internet. Text searches of the databases were ranked by relevance, where files with more keyword hits are listed first.
As the web grew in popularity, WAIS usage declined and eventually faded into obsolescence. The service has now been completely replaced by modern search engines.
How WAIS Functioned
A central server called the Directory of Servers stored and indexed a database of other publicly-available databases. Since data storage was limited by the technology of the day, databases were distributed amongst several servers. To conduct a WAIS search, one would connect via telnet to a server running a WAIS client or install and run their own client. Once connected to the Directory of Servers, a WAIS user could browse a large number of distributed databases, each focused on a specific topic (usually an academic discipline, such as history, biology, or social sciences).
WAIS was also popular as a way to search for text within individual Gopher servers. Modern search engines as a way to quickly find relevant information were inspired by WAIS. As the World Wide Web caught on and supplanted Gopher servers, WAIS declined in popularity.