Having root-level access to your server means that you will be able to view and change any file on it, which includes crucial system files. You may also install software that can update specific settings on the server throughout the, so the installation can be done only if you're signed in as the root user. The aforementioned has full privileges, i.e. you'll have full control over the machine at any time and you'll be able to perform anything you want. You may also create various other users either with similar rights or with fewer rights, according to what you require them for - day-to-day tasks, other server admins, etcetera. 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 via 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.