What does `@ConditionalOnMissingBean(PaymentClient.class)` mean on a default bean?

What does `@ConditionalOnMissingBean(PaymentClient.class)` mean on a default bean?

1. Register the default only when the condition finds no matching PaymentClient bean
2. Delete every application-defined PaymentClient and install the default
3. Create one default PaymentClient for every HTTP request
4. Disable all auto-configuration when PaymentClient is absent