Secure Shell uses the SSH protocol to authenticate and encrypt remote computer sessions.
SSH was designed as a secure replacement for older remote-login tools such as Telnet, which sends session data in plaintext. It protects the connection with encryption and can authenticate users with passwords, public-key credentials, or other methods.
SSH is widely used by system administrators, developers, and network engineers to operate remote servers. It can also create secure tunnels for other kinds of traffic and supports file-transfer tools such as SCP and SFTP.
SSH is sometimes confused with SFTP, but they are not identical. SSH is the underlying secure communications protocol, while SFTP is a file-transfer protocol that runs through an SSH connection.