Having root-level access to a server means that you can view and change any file on it, which includes crucial system files. You can also install software that can update certain settings on your server throughout the, so that the installation can be performed only if you are logged 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'd like. You can also generate other users either with similar rights or with fewer rights, depending on what you want them for - daily tasks, other server administrators, 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 you can do through other accounts. You can use a web-based graphical interface or a Secure Shell console to be able to connect to the server and to control it at the root level.