Having root-level access to your server means that you'll be able to view and modify any file on it, which includes essential system files. You can also set up software that can modify certain settings on the server during the process, so the installation can be performed only if you are signed in as the root user. The latter has full privileges, i.e. you will have full control over your machine whenever you want and you will be able to perform anything you need. You can also generate additional users either with similar rights or with fewer rights, depending on what you want them for - day-to-day tasks, other server administrators, etc. To be on the safe side, it's usually recommended to employ the root account only when you really need it and not for tasks you can do through other accounts. You can use a web-based graphical interface or a Secure Shell console to connect to the server and to manage it at the root level.