Also, as a part of a process designed to keep their work with you to the highest of standards, they may share some things that you say with other counsellors.

This video lasts for four minutes.

You may believe that your counsellor or therapist will keep everything that you say as confidential but it is not quite as simple or straightforward as that.  Under some circumstances a counsellor is obliged by law to disclose information about you, including some things that you may have said which you would consider to be confidential.