Secure Shell (SSH) is a cryptographic network communications 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. This service is generally used by Linux and is the linux/unix command line remote access solution that pairs well with 2FA and public/private key access. It is encrypted and has secure encrypted file sharing capabilities as well with SCP (Secure Copy) and even a windows client known as Putty (also free).
Related Terms: Cryptography, Private Key, Public Key
Source: The Secure Shell (SSH) Protocol Architecture, RFC 4252