If you have root-level access to a hosting server, this means that you'll have full control over it. In other words, you'll be able install any server-side app whatever the changes that it'll make to the software environment on your server, and you are able to both access and update any kind of file, which includes system files, and change any settings. This can be done by connecting to the server as a root user who has full privileges to perform all these things and to generate other users, which includes users that also have full privileges. This particular can be established through a web-based graphical interface or a Secure Shell console. For security reasons, it's recommended that you make a separate user for your everyday work and employ the root user only when you need to modify the server or to install software which may be needed by a script-driven application that you wish to run.