This paper focuses on techniques for retrieval used in information sciences and in World Wide Web search engines. The purpose of reference service and information science is to provide useful information in response to a query. The two metrics of recall and precision serve to express information retrieval performance. There are two major categories of searching tools on the Web: directories and search engines, and both require an indexing system. Building an index is done by either human or computer; for computers, the software program called a robot, or spider, or wanderer, visits each site and gathers information. Search engines on the Web incorporate a number of techniques to assist in both recall and precision. New trends in information retrieval include: artificial intelligence, probabilistic logic, query-by-example, query expansion, automatic summaries, natural language processing, which is a part of artificial intelligence, and concept-based searching. A description of the search engines available from Netscape's Net Search is provided at the end of this paper. (Contains 26 references.) (AEF)