Having root-level access to a server means that you'll be able to view and modify any file on it, which includes important system files. You may also install software that can change specific settings on your server throughout the, so the installation can be done only if you're logged in as the root user. The latter has full privileges, which means that you'll have full control over your machine at any time and you can do anything you'd like. You may also create other users either with the same rights or with fewer rights, depending on what you need them for - everyday tasks, other server administrators, etc. To be on the safe side, it is generally recommended to use the root account only when you really need it and not for tasks that can be done using other accounts. You may use a web-based graphical interface or a Secure Shell console in order to connect with the server and to control it at the root level.