Having root-level access to your server means that you can view and modify any file on it, which includes crucial system files. You can also set up software which can modify particular settings on the server throughout the, so that the installation can be performed only if you are signed in as the root user. The latter has full privileges, which means that you'll have full control over your machine whenever you want and you'll be able to perform anything you would like. You can also create other users either with similar rights or with fewer rights, depending on what you need them for - everyday tasks, other server admins, etc. 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 you can do using other accounts. You can use a web-based graphical interface or a Secure Shell console to be able to connect with the server and to manage it at the root level.