Having root-level access to your server means that you will be able to view and update any file on it, including crucial system files. You can also install software which can modify specific settings on your server throughout the, so that the installation is possible only if you're signed in as the root user. The aforementioned has full privileges, i.e. you will have full control over your machine at any time and you will be able to perform anything you need. You may also make various other users either with identical 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 actually 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 connect with the server and to control it at the root level.