Having root-level access to your server signifies that you can view and update any file on it, which includes important system files. You can also install software that can update specific settings on the server throughout the, so the installation can be performed only if you are signed in as the root user. The aforementioned 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 need. You can also make various other users either with similar rights or with fewer rights, based on what you require them for - daily tasks, other server admins, etc. To be on the safe side, it's usually recommended to use the root account only when you really need it and not for tasks which can be done via other accounts. You may use a web-based graphical interface or a Secure Shell console to connect to the server and to control it at the root level.