The document discusses SOA and NServiceBus. SOA aims to reduce coupling between systems through messaging and pub/sub. NServiceBus is a .NET messaging solution that uses an asynchronous distributed bus to enable loose coupling between services. It allows services to publish and subscribe to messages to communicate. NServiceBus provides benefits like scalability, durability, and improved developer productivity compared to traditional n-tier architectures. The document provides examples of how services can use events and handlers with NServiceBus to integrate and communicate asynchronously.