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