Key vs. Queue name in Rabbitmq (and why there both exist in @RabbitListener)

Question

I'm reading this article and it says that in message exchanges other than fanout , messages are routed to the queue that matches with their keys.

If this is true, then why there are two arguments ( value for @Queue and key ) in the following annotation? Isn't it enough to just specify the Queue name?

@RabbitListener(bindings = @QueueBinding(value = @Queue(value = RabbitMQConfiguration.AUTHENTICATION_EMAILS_QUEUE, durable = "true"), exchange = @Exchange(value = RabbitMQConfiguration.EMAIL_MESSAGE_EXCHANGE_NAME), key = "accountActivationEmail"))
public void receiveMessage(Map<String, String> message) {
    this.sendEmail(getEmail(message));
}

One more question: Having the annotation you saw for listeners, do I need to have a separate @Configuration class to specify MessageListenerAdapter , SimpleMessageListenerContainer , Binding , Exchange , Queue like the following:

@Configuration
public class RabbitMQConfiguration {

    public final static String AUTHENTICATION_EMAILS_QUEUE = "AUTHENTICATION_EMAILS_QUEUE";
    public final static String EMAIL_MESSAGE_EXCHANGE_NAME = "EMAIL_EVENTS";

    @Bean
    public Queue authenticationEmailsQueue() {
        return new Queue(AUTHENTICATION_EMAILS_QUEUE, false);
    }

    @Bean
    public DirectExchange emailMessagesExchange() {
        return new DirectExchange(EMAIL_MESSAGE_EXCHANGE_NAME);
    }

    @Bean
    public Binding authenticationEmailMQBinding(Queue queue, DirectExchange exchange) {
        return BindingBuilder.bind(queue).to(exchange).with(AUTHENTICATION_EMAILS_QUEUE);
    }

    @Bean
    public SimpleMessageListenerContainer authenticationEmailContainer(ConnectionFactory connectionFactory,
    MessageListenerAdapter listenerAdapter) {
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.setQueueNames(AUTHENTICATION_EMAILS_QUEUE);
        container.setMessageListener(listenerAdapter);
        return container;
    }

    @Bean
    public MessageListenerAdapter authenticationEmailHandlerAdapter(AuthenticationEmailHandler receiver) {
        return new MessageListenerAdapter(receiver, "receiveMessage");
    }

}