The pricing per user is usually per app – concurrent users can be viewed via metrics and named users refers to the number of accounts created on your app.
Hope this helps.
There are 2 types of users. Named & anonymous users.
Named users need a dedicated account in the app.
Which can either be created as local account → use the page account_Overview to manage them or create your own page based on the entity Account.
Or can be managed through a Identity provider using SSO.
Both cases a account record will be created in the app.
These are temporary accounts which are automatically created when someone accesses the app, without authentication and anonymous users have been enabled.
Both type of users count for your license depending on the type of licence.