Rsh

A Unix command that lets a user remotely log in to a server on the network and pass commands to it. It is similar to the rlogin command, but provides passing of command-line arguments to the command interpreter on the server at the same time. Rsh can be used within programs, as well as from the keyboard.

Rsh allows users remote access without having to re-authenticate. Ssh was designed to be a replacement for the unsecure rsh protocols. The advantages of Ssh lay in its use of strong encryption techniques to establish secure communications between a server and a client machine.