A specialized program that facilitates information retrieval from large segments of the Internet. Note 1: Search engines attempt to help a user locate desired information or resources by seeking matches to user-specified key words. The usual method for finding and isolating this information is to compile and maintain an index of Web resources that can be queried for the key words or concepts entered by the user. The indices are often built from specific resource lists, and may also be created from the output of Web crawlers, wanderers, robots, spiders, or worms. The indices are usually compiled during times of minimum network traffic. Note 2: Different engines are appropriate for different kinds of searches, and most can be optimized for specified results.