If you have root-level access to a hosting server, this means that you will have full control of it. That is to say, you'll be able set up any server-side application whatever the changes that it will make to the software environment on the server, and you'll be able to 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 who has full privileges to do the aforementioned things and also to make other users, including users that also have full privileges. The connection can be established with a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you create another user for your daily work and use the root user only when you have to customize the server or to set up software that may be required by some script-driven app that you would like to run.