Secure Shell, commonly known as SSH, is a cryptographic network protocol that is used to execute commands on a remote server or to exchange info between a web server and a client. Since the info exchanged by the 2 sides is protected, a third party can't intercept it, which makes SSH a preferred means of managing a hosting account. The commands which can be executed depend on the type of hosting service. On a shared server, for instance, the choices are limited as you simply won't have root access to the web server, so you could only create/move/delete files, set up and unpack archives, export and import databases, etcetera. These are all actions which are executed inside the shared hosting account and don't need a higher level of access. Through a virtual or a dedicated server, you shall have the ability to install server-side software or to restart the server or just a particular service (web server, database server, etc.). SSH commands are submitted with a command line, and if you don't use a UNIX-like Operating System, there are tons of applications for other OSs, which you can use to connect to the remote server as well.