App passwords or app-specific passwords are randomly generated passwords that are used for authentication. App passwords are required for accounts using two-factor authentication (2FA). Providers such as Nylas also require app passwords for third-party access.
An app password is required if 2FA is enabled and authenticating without a security code.
Yahoo Mail accounts require an app password for Nylas to authenticate. An app password gives Nylas access to the account through the single password login.
Apple ID uses an app password for accessing information in iCloud.
The following providers also require app passwords: