Having root-level access to a server means that you can view and modify any file on it, including crucial system files. You can also set up software which can update specific settings on the server during the process, so that the installation can be performed only if you're signed in as the root user. The aforementioned has full privileges, which means that you will have full control over your machine at any time and you will be able to do anything you would like. You can also make various other users either with similar rights or with fewer rights, depending on what you want them for - everyday tasks, other server admins, etcetera. To be on the safe side, it is generally recommended to employ the root account only when you really need it and not for tasks that 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 manage it at the root level.