Having full root-level access signifies that you can access and modify every file on a specific server, including all the system files, and to change system settings or set up server-side software which may be needed by specific scripts and even offline apps to work effectively. A server is accessed at the root level via a root user, which has full privileges to do all the aforementioned things. Your root user can also make various other users. For security reasons, you're advised to have another account for daily tasks and to use the root account only if you actually need to do a particular task on the website hosting server. The root-level access attribute gives you full control of your server from any kind of location, as long as you know the user credentials.