What is the purpose of the NCQRS.EventBus project

[Adam Greene]

I'm trying to figure out what the purpose of the EventBus project is.  Specifically what are Pipelines, how do you use them, how do they relate to the ElementStore's (what is an ElementStore's purpose), etc.  In looking at regenerating read models, people seem to use this project.  I'm just trying to better understand how it fits into the NCQRS landscape.