On my team at work, we use the IBM MQ technology a lot for cross-application communication. I\'ve seen lately on Hacker News and other places about other MQ technologies like Ra
MQ simply stands for Message Queue.
You would use one when you need to reliably send a inter-process/cross-platform/cross-application message that isn't time dependent.
The Message Queue receives the message, places it in the proper queue, and waits for the application to retrieve the message when ready.