When you're adding users to your account, you can choose four different roles: Administrator, Recruiter, Engineer, and Collaborator. You'll have a set number of Platform Users (Administrator, Recruiter, Engineer) and a separate number of Collaborators.
For a recruiter role, you can choose if the user should see all candidate data or only their candidates (recommended for external recruiters).
If you assign an engineer or collaborator role to a user, you can choose if they should see anonymized data. If anonymization is enabled, they will not see any PII of the candidate whether they’re logged into Codility, looking at their notification email, or viewing the shared report link. You can see more information on this here
Why do we have a separate limit on the number of Collaborators?
Collaborators have fewer permissions than the rest of the roles (i.e. they can't view account analytics) and are recommended to be used for users who need to interact with Codility only occasionally (to review a report or hold a CodeLive interview, for example). You can see more details about this role below.