This is one of the most useful pieces of any I really use is every day at work. So these are basically like queues or steroids. As unlike using your queues, you can actually close these, you can clone them. You can have multiple data waiting to receive something like workers. That's what we're really useful in practice. The nicest part here is that it can work across wrap streams. A very good example is that say you have a stream that is based on HTTP and you want to get the IP client IP address. This is something you can do transparently with this type attributes.