FTP stands for File Transfer Protocol. A protocol is a language that enables computers to speak to one another. FTP is used to make files and folders publicly available for transfer over the Internet. In some cases you may need to get permission from the network computer's administrator to log on and gain access to files on the computer. But often you'll find that you can use FTP to gain access to certain networks or servers without having an account, or being an official password holder, with that computer. These "anonymous" FTP servers can contain a broad range of data that is publicly available through FTP.
The Internet address (URL) for an FTP server looks slightly different from the URL you use for a typical Web page. For example, Microsoft has an "anonymous" FTP server at ftp://ftp.microsoft.com, where you can download files ranging from product fixes, updated drivers, and utilities, to Microsoft Knowledge Base articles and other documentation.
How much access you have to files and folders on FTP servers depends on whether you gain access to the servers through a CERN proxy server or directly, and what kind of permissions you have with the FTP server.