When you have root-level access to a hosting server, it means that you'll have full control of it. That is to say, you'll be able install any server-side application whatever the changes that it'll make to the software setting on the server, and you can both access and modify any file, including system files, and modify any settings. You can do this by connecting to the server as a root user that has full privileges to do all these things and to create other users, including 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 one more user for your everyday work and employ the root user only when you have to modify the server or to set up software that may be required by a script-driven application that you want to run.