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