请帮助我理解消息队列是如何工作的。

Been using PHP for quite some time now and I was wondering what this whole "message queue" is all about. Let's take facebook for example. I can update my status but then I have to show that status updates to all my friends (let's say I have 3000 followers). Even more work if there are comments and they have to be notified to all friends who left a comment via email. With the example I've seen, it appears that all a message queue does is take the "message" (my status update) and puts it into some temporary space (filesystem or DB table). I then have a cron job that pulls it out and updates my table. Been using PHP for quite some time now and I wa