[blep_]

It's messaging in the sense of message passing between processes. You put messages into it when you want them to be processed asynchronously.

They go into queues based on attributes of the messages ("routing keys") matched against rules you set up ("bindings").

Other things pick up messages off of those queues and process them.

When they're done, they acknowledge the message and it's removed from the queue. If they crash, the message doesn't get acknowledged and it goes back to the queue.