If you have root-level access to a server, it means that you will have full control over it. That is to say, you can set up any server-side application regardless of the changes that it'll make to the software environment on the server, and you will be able to both access and change any kind of file, which includes system files, and change 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, which includes users who also have full privileges. The connection can be established using a web-based graphical interface or a Secure Shell console. For security reasons, it is recommended that you create another user for your everyday work and use the root user only when you have to customize the server or to set up software which may be required by a script-driven application that you wish to run.