Not all FTP servers use the "anonymous server" principle. An anonymous server enables us to access clients without client authentication.
Since the FTP protocol did not take into account anonymous servers, FTP anonymous users have to set a username and password during their access to an FTP server. Generally, either the string anonymous or the string ftp is used as a username. Both strings have the same meaning. A user email address is often demanded as a password. This helps the anonymous server operator to create statistics concerned with access to the server.
Some anonymous servers allow access only to clients whose computers have the appropriate PTR record in the DNS. This restriction, however, has very disputable significance.
An anonymous FTP server serves users for downloading file, i.e., companies can offer free information using an anonymous FTP server. Anonymous FTP servers can be accessed very easily using Internet browsers.
If anonymous FTP servers...