Archie is a program that allows you to search the files of all the Internet FTP servers that offer anonymous FTP. Archie is actually an indexing spider that visits each anonymous FTP site, reads all the directory and file names, and then indexes them in one large index. A user can then query Archie, which checks the query against its index. To use Archie, you can Telnet to a server that you know has Archie on it and then enter Archie search commands. However, it's easier to use a forms interface on the Web called ArchiePlex.
Although Archie is often credited as being the Internet's first seach engine, it ultimately became less important with the growth of the World Wide Web. It was perhaps of most use for serious researchers who already know that the topic of their search is likely to be found on FTP servers. Veronica is a program similar to Archie that indexed and searched the files on Gopher servers.