A “Topic” in Moksha is basically just a message queue.
By abstracting out the low-level messaging protocols and brokers, Moksha applications can interact with “topics” without having to worry about the underlying protocols that are involved. For example, a topic could potentially be represented by a a STOMP destination, or even an AMQP message queue. These messaging backends can be swapped out and configured without having to alter the applications that care about those topics.
For details on how to interact with topics, see the documentation on Consumers, DataStreams, and the MokshaHub.