When you have root-level access to a hosting server, it means that you'll have full control over it. That is to say, you'll be able install any server-side application whatever the changes that it will make to the software environment on the server, and you can both access and customize any file, which includes system files, and change various settings. This can be done by connecting to the server as a root user which has full privileges to do the aforementioned things and also to make other users, which includes users who also have full privileges. This particular can be established with a web-based graphical interface or a Secure Shell console. For security reasons, it is recommended that you make one more user for your everyday work and use the root user only when you have to customize the server or to set up software that may be needed by a script-driven app that you would like to run.