Having root-level access to a server signifies that you'll be able to view and modify any file on it, which includes essential system files. You may also install software that can modify particular settings on your server throughout the, so the installation is possible only if you're 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 do anything you want. You may also create additional users either with similar rights or with fewer rights, based on what you want them for - everyday 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 you can do via other accounts. You can use a web-based graphical interface or a Secure Shell console in order to connect to the server and to manage it at the root level.