File transfer protocol is a method of transferring data over a network. On Ubuntu, FTP may be used in both GUI (though FTP clients) and CLI (through, e.g., the sftp command) modes.
FTP (File Transfer Protocol) is a fast and well-established method for transferring files. Today, users generally use Secure FTP (SFTP) which adds encryption, since normal FTP is sent using cleartext. To get around this obvious security problem, many FTP servers that can be used to transfer files over the internet are anonymous - allowing anyone to log in with a generic name (usually "anonymous") and a sometimes a meaningless password.
Basic CLI usage example with simplified output:
$ ftp ftp.gnu.org
Connected...
Name: anonymous #I enter anonymous to log in
ftp> ls #list files on the server
[long list in ls -l format]
ftp> lcd playground #I change directory on my local system
Local directory now /home/zanna/playground
ftp> get somefile.txt #I download a file to the selected local directory
Transfer complete
ftp> bye #I log off and exit ftp
$
Type help at the ftp> prompt for a list of supported commands.
