Messages are not published directly to a queue; instead, the producer sends messages to an exchange. An exchange is responsible for the routing of the messages to the different queues. An exchange accepts messages from the producer application and routes them to message queues with the help of bindings and routing keys. A binding is a link between a queue and an exchange:

Message flow in RabbitMQ

1. The producer publishes a message to an exchange. When you create the exchange, you have to specify the type of it. The different types of exchanges are explained in detail later on.
2. The exchange receives the message and is now responsible for the routing of the message. The exchange takes different message attributes into account, such as routing key, depending on the exchange type.

3. Bindings have to be created from the exchange to queues. In this case, we see two bindings to two different queues from the exchange. The exchange routes the message into the queues depending on message attributes.
4. The messages stay in the queue until they are handled by a consumer.
5. The consumer handles the message.