Having root-level access to a server signifies that you'll be able to view and change any file on it, including important system files. You can also set up software that can update particular settings on your server throughout the, so the installation can be done only if you're logged in as the root user. The aforementioned has full privileges, i.e. you will have full control over your machine at any time and you can perform anything you want. You can also make additional users either with the same rights or with fewer rights, depending on what you want them for - everyday tasks, other server admins, etc. To be on the safe side, it's usually recommended to employ the root account only when you really 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 be able to connect with the server and to manage it at the root level.