OpenSSH is the free version of SSH (Secure Shell).
SSH is a cryptographic protocol for performing the following tasks:
Login on a remote computer
Interactive/non-interactive command execution on a remote computer
File transfer between different computers in a network
Tunneling of unsecured TCP protocols over an encrypted SSH connection
SSH refers not just to the protocol itself but also to its concrete implementations.
OpenSSH is the secure alternative to the r utilities rlogin, rcp and rhs and the programs telnet and ftp, provided these programs are not secured with TLS. In contrast to the aforementioned programs, OpenSSH encrypts all network traffic (including passwords) and thus prevents eavesdropping, connection hijacking, and other attacks at network level. Furthermore, OpenSSH supports a raft of tunneling variants and a wide range of authentication methods.