Having root-level access to a server means that you'll be able to view and update any file on it, which includes crucial system files. You may also install software that can modify particular settings on the server throughout the, so the installation is possible only if you're signed in as the root user. The latter has full privileges, which means that you'll have full control over your machine whenever you want and you'll be able to do anything you need. You can also generate various other users either with identical rights or with fewer rights, according to what you want them for - daily tasks, other server administrators, etcetera. To be on the safe side, it's usually recommended to employ the root account only when you actually need it and not for tasks that can be done via other accounts. You can use a web-based graphical interface or a Secure Shell console to connect with the server and to control it at the root level.