If you have root-level access to a server, it indicates that you will have full control of it. That is to say, you can set up any server-side app whatever the changes that it'll make to the software environment on the server, and you will be able to both access and change 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 perform the aforementioned things as well as to make other users, including users that also have full privileges. This connection can be established using a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you make another user for your everyday work and employ the root user only when you need to modify the server or to set up software which may be required by a script-driven application that you would like to run.