Having root-level access to your server means that you will be able to view and modify any file on it, which includes essential system files. You may also set up software that can update certain settings on your server during the process, so that the installation is possible only if you are signed in as the root user. The aforementioned has full privileges, i.e. you'll have full control over the machine at any time and you can perform anything you need. You can also make additional users either with identical rights or with fewer rights, depending on what you require them for - everyday 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 using other accounts. You can use a web-based graphical interface or a Secure Shell console in order to connect with the server and to control it at the root level.