SSH stands for Secure SHell, and is basically a way to access the server remotely, but with all the functionality of actually sitting in front of it. As the copy of Linux installed on server is text based only, there is no graphical option here! So, proceed with caution, as you could destroy your files or user directory (it's not possible to destroy anything else outside of your home directory though)
Most people will never need to access the command line of the server to manage their accounts, but it's nice to have the facility there!