Answer Description
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.
Wikipedia
Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH SSH provides a secure channel over an unsecured network by using a client–server architecture, connecting an SSH client application with an SSH server The protocol specification distinguishes between two major versions, referred to as SSH-1 and SSH-2 The standard TCP port for SSH is 22 SSH is generally used to access Unix-like operating systems, but it can also be used on Microsoft Windows Windows 10 uses OpenSSH as its default SSH client
Secure_Shell - Wikipedia, the free encyclopedia