In OS X, what is a postgres group under accounts?

I have turned on features so that I can share screens within my network between two macs but I never manually created this group, which now shows up in system prefs under accounts, then groups. I’m guessing that it is something that is automatically created for the purposes of sharing but I want to make sure someone is not trying to login remotely to my computers, since I did not manually create this group. Additionally, when I look at the members of the group, my normal user accounts seem to not be selected, but there is an unlabelled account that is selected as a member of this group. Any thoughts would be welcome- thank you!