Publish/Subscribe
also called Pub/Sub
A messaging pattern where each published message is delivered to every interested subscriber, rather than to one competing worker.
The contrast that matters is with point-to-point queueing. In a queue, one message goes to one consumer — that is work distribution. In pub/sub, one message goes to all subscribers — that is notification. Using the wrong one is a common and confusing bug: five instances of a service subscribed to a topic will each process every message, sending five emails.
Most brokers give you both, and the shape is usually "topic fans out to one queue per consumer group, competing consumers within the group". That combination — broadcast between groups, distribute within a group — is what production systems actually want.
Subscribers must be independently failable: a slow or dead subscriber must not block delivery to the others, which means per-subscriber queues and per-subscriber dead-lettering rather than a shared cursor.