What does TurboTax agent see during screen share on a desktop? Do they see EVERYTHING on a desktop or just the TurboTax software data?

Does sharing the desktop screen with a TurboTax agent display everything that is on the desktop or just data within the TurboTax software?  Supposedly, I am talking to an agent on the phone and sharing my screen, can I open my browser to view personal information without the agent being able to view the browser information?  Thank you.