Q:

What is a servicebus?

I've read about nservicebus countless times on the net, but still don't get what a service bus is.
All I think is it is a way for very disparate systems to talk to each other? In which case, I don't see why it is any better than WCF?
I've seen the thread on here about what a service bus is but it still hasn't clicked.
Thanks

A:

Assuming that you have read these pages http://particular.net/nservicebus and http://docs.particular.net/nservicebus/architecture/nservicebus-and-wcf you'll find that NServiceBus makes communicating with services much easier. 
It wraps WCF by taking care of the poisoned and transactional elements of messaging as well as offering out of the box Pub / Sub style messaging. Benefits that NServiceBus will take care of include:

Long-running stateful processes Using WF on top 
On-premise messaging   
Client can send messages if server is offline  
Poison message detection and dispatching 
Poison messages re-processing 
Subscriptions persist after restart 
Polymorphic message dispatch 
Polymorphic message routing
Message-driven unit testing

