I am rather new to Star Trek but I have to say I am quite an avid fan. I have recently started watching The Next Generation and I have noticed in the first season there is a man who walks around in a Starfleet gown. I was curious as to why and what purpose this serves. I have included a picture. This is a screenshot from episode 11001001.
Thank you very much for any light you can shine on the subject. Speculations are completely welcome.