Having full root-level access signifies that you'll be able to access and modify every file on a particular server, which includes all system files, and to change system settings or install server-side software which may be necessary for certain scripts and even offline apps to work appropriately. A server is accessed at the root level via a root user, which has full privileges to perform all the aforementioned things. Your root user may also generate other users. For safety reasons, you're advised to have one more account for everyday tasks and to use the root account only if you actually need to perform some task on the hosting server. The root-level access attribute will provide you with full control of your server from almost any location, as long as you have the user credentials.