If you have root-level access to a hosting server, it means that you will have full control over it. In other words, you can set up any server-side application irrespective of the changes that it'll make to the software environment on the server, and you are able to both access and change any file, including system files, and change various settings. You can do this by connecting to the server as a root user which has full privileges to perform all these things as well as to make other users, including users who also have full privileges. This connection can be established using a web-based graphical interface or a Secure Shell console. For security reasons, it's recommended that you make another user for your daily work and employ the root user only when you need to modify the server or to set up software that may be required by some script-driven application that you want to run.