SSH means Secure Shell Protocoll; It's like telnet, but with strong encryption, so there's no fear of hackers or crackers sniffing on your network stream.
Normally, you need a terminal program which supports SSH, like putty or SecureCRT, among others. However, if you don't want to install software and/or don't have the time, this java applet does it's job very well.
Be sure to click "OK" when your browser asks you if you want to enable this applet!