When you have root-level access to a hosting server, it indicates that you'll have full control over it. That is to say, you can install any server-side app whatever the changes that it will make to the software environment on the server, and you will be able to both access and change any kind of file, which includes system files, and change various settings. This can be done by connecting to the server as a root user which has full privileges to perform all these things as well as to generate other users, which includes users that also have full privileges. The connection can be established through a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you make another user for your daily work and use the root user only when you need to customize the server or to set up software which may be needed by some script-driven application that you want to run.