When using text base FTP clients such as ftp on from a DOS prompt or on UNIX command line you ACTUALLY converse with the server with commands that are very close to the FTP protocol.
Let is study how we use such simple FTP applications first as they are sometimes very useful to use (over a Telnet client for example) and we can gain a good appreciation of what is required before we look at the actual FTP PROTOCOL.
You can actually see the PROTOCOL in operation of you use the debug command option (see below).