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