In the Identity Mapping window, you choose the type of name identifier your partner requires. Your selection might affect the way that the service provider (SP) looks up and associates your users at the SP site. You and the SP should decide in advance which option to use.
The Identity Mapping window does not apply for connections using the WS-Federation protocol in conjunction with JSON web token (JWT)-based single sign-on (SSO) tokens. Instead, work with the SP to define an attribute contract that it can use to map users to accounts at the SP site.