Secure Shell, commonly known as SSH, is a cryptographic network protocol employed to execute commands on a remote machine or to exchange data between a hosting server and a client. Since the information exchanged by the 2 sides is encrypted, a 3rd party can't intercept it, which makes SSH a favored means of handling a hosting account. The commands that can be executed depend on the type of hosting service. On a shared server, for instance, the alternatives are limited as you won't have root access to the website hosting server, so you can simply create/move/delete files, set up and unpack archives, export and import databases, etcetera. They're all actions that are executed in the shared hosting account and don't require a higher level of access. With a virtual or a dedicated server, you shall be able to set up server-side software or to restart the machine or just a particular service (web server, database server, etc.). SSH commands are submitted with a command line, and if you don't employ a UNIX-like OS, there are a number of applications for other OSs, which you can use to connect to the remote hosting server as well.