These events are published by the Ordering context and subscribed to by other contexts, allowing them to react to changes.
You can find more information on Domain-Driven Design in Eric Evans' book, which is available in various formats, including PDF. domain driven design eric evans ebook pdf 51
You decide to apply Domain-Driven Design principles to tackle the complexity. You start by identifying the core business domains: Ordering, Inventory, and Customer Management. These events are published by the Ordering context