Having root-level access to a server signifies that you can view and update any file on it, including essential system files. You may also set up software that can change specific settings on your server during the process, so that the installation can be done only if you are logged in as the root user. The latter has full privileges, i.e. you will have full control over your machine at any time and you will be able to perform anything you want. You may also make other users either with identical rights or with fewer rights, according to what you require them for - daily tasks, other server administrators, etc. To be on the safe side, it's usually recommended to employ the root account only when you actually need it and not for tasks that can be done via other accounts. You can use a web-based graphical interface or a Secure Shell console to connect to the server and to control it at the root level.