Superusers are administrative users within a team, and have full access to all of CaptionHub's functionality inside of that team.
Producers are administrative users within a project. They have to be assigned to specific projects, by a Superuser. 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.
Optionally, Producers may be given the power to create projects. In such cases, they'd automatically be assigned to those projects as a producer.
Language supervisors have a similar permissions profile to a producer, but restricted to the language that they're the language supervisor for.
Linguists can translate language versions. They belong to a team, and are marked as having competency in specific languages. They can only be assigned to language versions that are part of projects in their team, and that they have proficiency in the language of. Unless a linguist is specifically assigned to a language version, they won't be able to see it.
Reviewers are very similar to a linguist, but they can be assigned to workflows which include a review step. If workflows include a review step, then linguists are unable to approve their own work. Instead, they'll submit captions for review by a reviewer. See more on workflows here.