User roles in POEditor are centered around the localization project. A user can have one of the following roles in a project: owner, admin or contributor (with or without proofreading rights).
This is the user who hosts the localization project. As project owner, you have all the possible privileges in the localization projects you host on your account (these are the project which do not have the 'Shared' label on your Dashboard).
The strings added to your localization projects are counted against your plan's limit.
An admin is a POEditor user appointed by the project owner to manage the translation and localization process.
Admins can be added in in the project's Settings, and can do almost everything the project owner can do in the localization project, with a few exceptions: they can't delete the projects they're managing or add/delete other administrators to/from them.
By default, admins have access to all the languages in the localization project.
Also worth noting is that admins don't see in their integrations page the project they administrate. They also can't purchase a subscription to increase the localization project's string limit (unless the owner also sets them as Alternative Payer for their account).
This is the translator's role. Contributors are added to the localization project by the owner or by an admin in the project page (in Languages). They have access only to the languges they are assigned to and cannot add or remove terms. They also cannot order translations.
Contributors can also self-enroll to a localization project if this project is public.
In the project's Settings, the owner and admins can enable Proofreading and then give contributors Proofreader rights.
Alternative payers are POEditor users assigned to pay for another user's subscription. They're not required to have any of the above roles in the localization project and can pay for more than one account. Payers have a tab in their account's billing section for each account they've agree to pay for.