The doctor committed a 'breach of confidentiality'. [=the doctor told another person private information about a patient]
All medical records are treated with complete 'confidentiality'. [=are kept completely private]
Someone was leaking 'confidential' information [=telling secrets] to the press.
(..) And it'll make me very happy if she loses. I wonder if I could talk to you? Go ahead. Isn't there some other place? It's rather confidential, what I have to say. - In my office. - Right. You know it's very important I get out of Casablanca. (..)1942 Casablanca