I touched on this topic in my First Day with Ubuntu at the Office post under Accessing Remove File Systems; however, I thought that this deserved its own topic.
For those that don’t know SSH stands for Secure SHell. In very non-technical terms, SSH allows you to access a system running a SSH server over a network. This other system can be another computer in your home or a remote system on the other side of the planet. SSH will allow you to connect to that other system and communicate with it securely. All the data passed back and forth is encrypted, so you don’t have to worry about people sniffing your passwords or valuable data.
You may be asking what all of that means to you. What it means is that you can connect to and control a computer that is somewhere else with the computer that is sitting right in front of you. If you have a remote webserver running Linux, SSH will let you install software, edit files, change the server configuration, access the database, and more. Did you forget a file on your computer at home? No problem, just SSH into your home computer and send the file to your email account or copy it directly to your office computer.
Hopefully those quick examples of what you can do is enough to whet your appetite.