Having root-level access to your server signifies that you will be able to view and change any file on it, including essential system files. You may also set up software that can change certain settings on the server throughout the, 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 the machine at any time and you'll be able to perform anything you want. You may also create additional users either with identical rights or with fewer rights, according to what you want them for - daily tasks, other server admins, 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 through 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.