When you have root-level access to a hosting server, this means that you will have full control over it. That is to say, you'll be able install any server-side app regardless of the changes that it'll make to the software environment on your server, and you're able to both access and customize any kind of file, including system files, and modify any settings. This can be done by connecting to the server as a root user that has full privileges to do all these things as well as to generate other users, including users that also have full privileges. This connection can be established with a web-based graphical interface or a Secure Shell console. For security reasons, it's recommended that you make a separate user for your daily work and employ the root user only when you have to modify the server or to install software that may be needed by a script-driven app that you'd like to run.