Linguists are the main users of CaptionHub. They translate caption sets. They belong to a team, and are marked as having competency in specific languages. They can only be assigned to caption sets that are part of projects in their team, and that they have proficiency in the language of.
Producers are administrative users within a project. They have to be assigned to specific projects. Within a project they are assigned to, they can add and remove users from caption sets, invite users to the project, hand caption sets between users, and download completed files. They cannot translate caption sets.
Superusers are administrative users within a team. They have all the power of Producers; in addition, they can create Projects and edit any caption-set they like. They only have these powers within the team they lead.
All users may belong to many teams - they may, for instance, be freelance. A user can only see users that belong to teams they do, and they will not be able to see if they're a member of other teams. If you see that a user is in more than one team, it is because you are in those teams as well.
Superusers can only lead one team.