Having full root-level access signifies that you'll be able to access and customize every file on a specific server, which includes all system files, and to change system settings or install server-side software which may be required by certain scripts and even offline applications in order to function effectively. A server is accessed at the root level with a root user, which has full privileges to perform all of the abovementioned things. Your root user may also make other users. For safety reasons, you're advised to have a separate account for daily tasks and to use the root account only if you actually need to perform a task on your hosting server. The root-level access attribute will give you full control of your server from any location, provided that you know the user credentials.