There is a difference between the publish/subscribe and producer/consumer models.
Publish/Subscriber: Subscribers subscribe to the publisher. Each message the Publisher publishes is sent to all the subscribers. That is, all subscribers receive the same message. (Think of a newspaper or magazine subscription. All subscribers receive the same magazine or newspaper)
Producer/Consumer: Each message the producer produces will be consumed by a single consumer. This is a mechanism to distribute the workload to multiple consumers. (Think of the several cash registers at the supermarket. Each customer goes to a single cash register. The customers are like the messages that are produced and the cash registers are the consumers)