When you have root-level access to a server, it means that you'll have full control of it. In other words, you'll be able install any server-side app irrespective of the changes that it'll make to the software setting on the server, and you are able to both access and change any file, which includes system files, and modify any settings. This can be done by connecting to the server as a root user who has full privileges to do all these things as well as to generate 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 create one more user for your everyday work and use the root user only when you need to customize the server or to set up software that may be needed by a script-driven app that you would like to run.