Identity verification settings refer to the settings for "Authentication by email", "Biometric authentication, Passcode authentication, etc", and "Authentication by app".
In addition to your Expo ID/password, these can be used for authentication at login to increase the security.
You are only required to set it up the first time you log in.

ExpoID Registration Manual:

https://www.expo2025.or.jp/wp/wp-content/themes/expo2025orjp_2022/assets/pdf/tickets-index/id_registration_manual_en.pdf