Having root-level access to your server signifies that you will be able to view and change any file on it, including important system files. You can also install software which can change certain settings on your server during the process, 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 will have full control over your machine at any time and you can do anything you need. You may also generate other users either with identical rights or with fewer rights, based on what you require them for - day-to-day tasks, other server admins, etc. 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 using other accounts. You may use a web-based graphical interface or a Secure Shell console in order to connect to the server and to control it at the root level.