When you have root-level access to a hosting server, it means that you will have full control of it. In other words, you'll be able install any server-side app no matter what the changes that it'll make to the software setting on the server, and you are able to both access and modify any file, which includes system files, and modify various settings. This can be done by connecting to the server as a root user which has full privileges to do the aforementioned things as well as to create 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 create one more user for your everyday work and employ the root user only when you need to customize the server or to set up software that may be needed by a script-driven app that you want to run.