If you have root-level access to a hosting server, it indicates that you'll have full control of it. In other words, you'll be able set up any server-side application whatever the changes that it'll make to the software setting on your server, and you're able to both access and modify any kind of file, including system files, and change any settings. This can be done by connecting to the server as a root user that has full privileges to perform the aforementioned things and also to create 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 use 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'd like to run.