When you have root-level access to a hosting server, it indicates that you will have full control of it. That is to say, you'll be able set up any server-side app whatever the changes that it'll make to the software setting on your server, and you can both access and modify any kind of file, including system files, and change any settings. You can do this by connecting to the server as a root user who has full privileges to perform the aforementioned things and to make other users, including users that also have full privileges. This particular can be established using a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you create a different user for your everyday work and use the root user only when you need to customize the server or to set up software which may be needed by some script-driven app that you want to run.