Secure Shell, better known as SSH, is a cryptographic network protocol employed to execute commands on a remote server or to exchange info between a web server and a client. As the data exchanged by the two sides is encrypted, a 3rd party can't intercept it, which makes SSH a favorite means of handling a web hosting account. The commands that could be executed are determined by the type of hosting service. On a shared hosting server, for example, the alternatives are limited as you will not have root access to the machine, so you may only create/move/delete files, set up and unpack archives, export and import databases, and so forth. They are all actions that are performed inside the shared hosting account and do not require 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, but if you don't employ a UNIX-like Operating System, there are tons of applications for other OSs, that you can use to connect to the remote hosting server as well.