Having root-level access to your server means that you will be able to view and update any file on it, which includes crucial system files. You may also install software which can change specific settings on the server throughout the, so that the installation can be performed only if you're signed in as the root user. The latter has full privileges, i.e. you will have full control over the machine at any time and you will be able to do anything you want. You can also generate various other users either with similar rights or with fewer rights, according to what you want them for - day-to-day 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 through other accounts. You can use a web-based graphical interface or a Secure Shell console to be able to connect to the server and to control it at the root level.