Access to anything that requires a password or authentication will not be accessible unless YOU type in the password. You and the technician will see the same thing, so if the technician opens a file that you're not comfortable sharing with them, you can tell them so or end the session yourself.
There are a few instances where the technician can request information from your computer (for example, system information about your operating system, amount of memory installed, etc.), but they won't have access to that information until you click Allow (in the Bomgar chat window) to grant that specific request.
Because the technician will be able to see any open documents on your screen, we strongly recommend that, before accepting the Bomgar session, you close all documents and applications that contain confidential information, or that are not relevant to the issue being resolved.