Add acknowledgement explanation
Fix
@@ -79,7 +79,7 @@ Client libraries provide listener implementation for consumers. For example, the
### Acknowledgement
-When a consumer has consumed a message successfully, the consumer sends an acknowledgement request to the broker, so that the broker will discard the message. Otherwise, it [stores](concepts-architecture-overview.md#persistent-storage) the message.
+When a consumer has consumed a message successfully, the consumer sends an acknowledgement request to the broker. This message is permanently [stored](concepts-architecture-overview.md#persistent-storage) and then it is deleted only after all the subscriptions have acknowledged it. If you want to store the message that has been acknowledged by a consumer, you need to configure the [message retention policy](concepts-messaging.md#message-retention-and-expiry).
Messages can be acknowledged either one by one or cumulatively. With cumulative acknowledgement, the consumer only needs to acknowledge the last message it received. All messages in the stream up to (and including) the provided message will not be re-delivered to that consumer.
