Having root-level access to your server means that you'll be able to view and update any file on it, including essential system files. You may also install software which can update particular settings on the server throughout the, so that the installation can be performed 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 whenever you want and you'll be able to perform anything you would like. You can also generate additional users either with identical rights or with fewer rights, depending on what you need them for - day-to-day tasks, other server admins, etc. To be on the safe side, it is usually recommended to use the root account only when you really need it and not for tasks which can be done through 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.