Having root-level access to your server means that you can view and modify any file on it, which includes crucial system files. You may also install software that can modify certain settings on the server throughout the, so the installation can be done only if you are logged in as the root user. The latter has full privileges, which means that you'll have full control over your machine whenever you want and you will be able to perform anything you'd like. You can also generate additional users either with identical rights or with fewer rights, according to what you require them for - everyday tasks, other server administrators, etcetera. To be on the safe side, it's usually recommended to use the root account only when you actually need it and not for tasks you can do via other accounts. You may use a web-based graphical interface or a Secure Shell console to be able to connect with the server and to control it at the root level.