If you have root-level access to a hosting server, it indicates that you will have full control of it. That is to say, you can install any server-side application whatever the changes that it will make to the software environment on your server, and you'll be able to both access and modify any file, including system files, and change various settings. You can do this by connecting to the server as a root user that has full privileges to do all these things and also to create other users, including users that also have full privileges. The connection can be established with a web-based graphical interface or a Secure Shell console. For safety reasons, it is recommended that you create another user for your everyday work and employ the root user only when you have to customize the server or to set up software which may be needed by some script-driven application that you want to run.