Secure Shell (SSH) is a cryptographic network protocol used for secure data communication, specifically to provide secure command-line access to a remote server. It operates on the default port 22. SSH ensures data integrity and confidentiality by encrypting the entire session between the client and server. HTTP and HTTPS operate on ports 80 and 443 respectively and facilitate web communication rather than command-line access. FTP (operating on ports 20 and 21) is used for file transfers, and even though it has variants that offer encryption, it does not provide a secure command-line interface like SSH does.