Your supervisor is most likely describing SSH (Secure Socket Shell) which is protocol that allows secure access to servers. Functionally SSH is very similar to telnet but is encrypted for added security. SSH can also be used to encrypt any text based communication, for example SSH-FTP is FTP using SSH for encryption.
Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. The best known example application is for remote login to computer systems by users.
SSH provides a secure channel over an unsecured network in a client-server architecture, connecting an SSH client application with an SSH server. Common applications include remote command-line login and remote command execution, but any network service can be secured with SSH. The protocol specification distinguishes …