A non-disclosure agreement is a legal agreement between at least two parties that describes sensitive information and material that they desire to communicate with one another for certain purposes but not with a third party. It also establishes a confidential connection between the parties in order to safeguard any sensitive or proprietary information. It safeguards nonpublic corporate data.

I feel there is no way to gauge about how much information is shared when one signs a NDA. It is based on who is signing the agreement. For example, a company most likely will not tell you their top-secret information if you are going for an interview. If you walk past production lines or research areas on your way to the interview, those may not be as secretive, but still are to some extent. I believe there would have to be some form of access level required to reach different areas and would have to sign several NDA’s as the access is granted.