Having root-level access to a server signifies that you will be able to view and update any file on it, including essential system files. You may also set up software which can change particular settings on the server throughout the, so that the installation can be performed only if you're 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 will be able to perform anything you want. You can also create additional users either with the same rights or with fewer rights, depending on what you want them for - everyday 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 can be done using other accounts. You can use a web-based graphical interface or a Secure Shell console to connect with the server and to control it at the root level.