Having root-level access to your server means that you will be able to view and change any file on it, including crucial system files. You can also install software that can change specific settings on the server during the process, so that the installation can be done only if you are logged in as the root user. The aforementioned has full privileges, i.e. you will have full control over the machine at any time and you'll be able to do anything you'd like. You may also make various other users either with similar rights or with fewer rights, based on what you require 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 you can do via other accounts. You can use a web-based graphical interface or a Secure Shell console in order to connect with the server and to manage it at the root level.