Having root-level access to a server means that you can view and modify any file on it, which includes crucial system files. You can also install software that can update specific settings on the server throughout the, so that the installation can be performed only if you are signed in as the root user. The aforementioned has full privileges, which means that you'll have full control over your machine at any time and you can perform anything you would like. You may also create various other users either with identical rights or with fewer rights, depending on what you need them for - everyday tasks, other server admins, etcetera. To be on the safe side, it's generally recommended to use the root account only when you really need it and not for tasks which can be done using other accounts. You may use a web-based graphical interface or a Secure Shell console to connect with the server and to control it at the root level.