SSH (Secure Shell) is a protocol for encrypting and securing various kinds of data transfers over a network or the Internet. SSH works by opening a secure channel between the SSH server and an authenticated user's computer. Many kinds of data may be sent or retrieved through this channel.
SSH can be understood as a large pipe: its purpose is to carry whatever is passed through it from one place to another without letting anything leak in or out.
WS_FTP Server with SSH uses SFTP (Secure File Transfer Protocol) over SSH2 to transfer files.
SFTP operates nearly identically to FTP, but all transmissions are secured under the SSH protocol.