If you have root-level access to a hosting server, this means that you'll have full control of it. That is to say, you can install any server-side application regardless of the changes that it will make to the software environment on your server, and you can both access and change any kind of file, which includes system files, and change any settings. This can be done by connecting to the server as a root user which has full privileges to perform all these things and also to create other users, including users that also have full privileges. The connection can be established using a web-based graphical interface or a Secure Shell console. For security reasons, it's recommended that you create another user for your everyday work and use the root user only when you need to customize the server or to install software that may be required by some script-driven application that you want to run.