If you have root-level access to a server, it means that you will have full control over it. In other words, you'll be able set up any server-side application whatever the changes that it will make to the software setting on your server, and you can both access and modify any file, including system files, and modify various settings. You can do this by connecting to the server as a root user that has full privileges to perform the aforementioned things and also to make other users, including users that also have full privileges. This particular can be established through a web-based graphical interface or a Secure Shell console. For safety reasons, it is recommended that you make another user for your daily work and employ 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'd like to run.