Having root-level access to a server signifies that you will be able to view and update any file on it, which includes important system files. You can also set up software which can modify specific settings on the server during the process, so the installation can be done only if you are signed in as the root user. The aforementioned has full privileges, i.e. you will have full control over your machine at any time and you can perform anything you need. You may also generate other users either with the same rights or with fewer rights, according to what you need them for - daily tasks, other server administrators, etc. To be on the safe side, it is usually recommended to use the root account only when you actually need it and not for tasks that you can do via 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.