When you have root-level access to a hosting server, it 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 your server, and you will be able to both access and change any file, including system files, and change various settings. This can be done by connecting to the server as a root user that has full privileges to do all these things and also to generate 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 safety reasons, it is recommended that you make a separate user for your everyday work and employ the root user only when you need to customize the server or to install software which may be required by a script-driven app that you want to run.