When you have root-level access to a hosting server, it means that you'll have full control of it. In other words, you can set up any server-side app irrespective of the changes that it will make to the software environment on the server, and you'll be able to both access and change any file, which includes system files, and change any settings. This can be done by connecting to the server as a root user which has full privileges to perform all these things and also to make 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 is recommended that you make a separate user for your everyday work and use the root user only when you have to customize the server or to set up software which may be required by a script-driven app that you want to run.