Having root-level access to a server signifies that you will be able to view and change any file on it, including essential system files. You can also set up software that can modify particular settings on the server during the process, so that the installation can be done only if you're signed in as the root user. The aforementioned has full privileges, i.e. you will have full control over your machine at any time and you can perform anything you need. You may also make additional users either with identical rights or with fewer rights, based on what you need them for - day-to-day tasks, other server admins, etc. To be on the safe side, it is usually recommended to use the root account only when you actually need it and not for tasks that can be done through other accounts. You may use a web-based graphical interface or a Secure Shell console to connect to the server and to manage it at the root level.