Import an existing user (from another database)

This username exists because it is being used with another database; using it with the current database requires it to be imported.

Note that technically any existing PostgreSQL "role" that is to be used as a username needs to be imported this way, regardless of whether it is a username in a different database.
Creates a new user
This username must not be used by any of the other databases. If you want to use a username that is already used with another database, you can do so by selecting the Import option.