AMQP is a wire-level messaging protocol that describes the format of the data that is sent across the network. If a system or application can read and write AMQP, it can exchange messages with any other system or application that understands AMQP, regardless of the implementation language.
WSO2 ESB provides the RabbitMQ AMQP transport, which allows you to send or receive AMQP messages by calling an AMQP broker (RabbitMQ) directly without the need to use different transport mechanisms, such as JMS.
For information on other ways to use AMQP with WSO2 ESB, see this article.