Having full root-level access means that you will be able to access and update every file on a specific server, which includes all the system files, and to change system settings or set up server-side software which may be necessary for certain scripts and even offline apps to function appropriately. A server is accessed at the root level through a root user, which has full privileges to perform all of the abovementioned tasks. The root user may also create other users. For security 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 website hosting server. The root-level access attribute will give you full control of your server from any location, given that you know the user credentials.
