If you have root-level access to a hosting server, this means that you'll have full control over it. In other words, you'll be able set up any server-side app whatever the changes that it'll make to the software setting on the server, and you are able to both access and customize any kind of file, including system files, and modify any settings. You can do this by connecting to the server as a root user which has full privileges to do the aforementioned things and also to generate other users, including users who also have full privileges. The connection can be established using a web-based graphical interface or a Secure Shell console. For safety reasons, it is recommended that you create a different user for your everyday work and employ the root user only when you have to customize the server or to install software that may be needed by some script-driven application that you would like to run.