How does an FTP work? 

 
FTP (File Transfer Protocol) is a standard network protocol used for transferring files from one host to another over a TCP-based network, such as the Internet. FTP works by establishing a connection between an FTP client and an FTP server, and allowing the client to upload or download files from the server. The client and server use a series of commands and responses to initiate and complete the file transfer. The FTP protocol also provides mechanisms for authentication, so that only authorized users can access the server's files.