When you have root-level access to a hosting server, it indicates that you will have full control of it. In other words, you'll be able install any server-side app whatever the changes that it'll make to the software setting on your server, and you're able to both access and update any kind of file, which includes system files, and modify any settings. This can be done by connecting to the server as a root user which has full privileges to do all these things and to create other users, which includes users who 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 one more user for your everyday work and use the root user only when you have to customize the server or to install software which may be needed by some script-driven application that you'd like to run.