Remote login, file transfer, and shell commands over a secure, encrypted connection. Also X and other tunneling. Web version at MindTerm . A substitute for poor security planning. The ultimate answer to your problems.
Most options work with ssh as with slogin .
This can be good and bad. This allows you a password-less login from local to remote. Greatly increases your level of security, but can affect ease of use. Prevents automated scripts using scp . X events to local ssh client.