In this video you can see how to make your blog posts public or private. Public posts could be to your internshiphost, fellow workers, peers, network that could comment on your work, thoughts. Private posts could be reflections, problems, questions for yourself that you also want to share with your 4.semester supervisor.
You can also make the whole blog private and then only give access to specific WordPress users e.g. your supervisor.
By adding a WordPress user (part of the wordpress community) to your blog other users can contribute with new posts and also see your private posts.
You could also make a very private blog or document on your local computer where only you have access