Having root-level access to a server means that you will be able to view and change any file on it, including essential system files. You can also install software which can change particular settings on the server during the process, so that the installation can be performed only if you are signed in as the root user. The aforementioned has full privileges, which means that you will have full control over the machine whenever you want and you can do anything you would like. You can also create other users either with the same rights or with fewer rights, according to what you require them for - daily tasks, other server admins, etcetera. To be on the safe side, it is usually recommended to employ the root account only when you really 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 in order to connect with the server and to control it at the root level.