SSH (Secure Shell) is a network protocol for remote access to another computer. The connection between the two machines is encrypted, which prevents exchanged information to be intercepted by another computer on the network. SSH access is one of the safest ways for remote connection to another machine.
SSH access is most commonly used to manage and administer servers with Linux-based system such as virtual private servers (VPS).
Read more: First steps in Secure Shell (SSH) | Blog