There's an important distinction between services that deliver an event and services that deliver a message.
An event is a lightweight notification of a condition or a state change. The publisher of the event has no expectation about how the event is handled. The consumer of the event decides what to do with the notification. Events can be discrete units or part of a series. An event - SOMETHING HAS HAPPENED.
An example, an event notifies consumers that a file was created. It may have general information about the file, but it doesn't have the file itself.
A message is raw data produced by a service to be consumed or stored elsewhere. The message contains the data that triggered the message pipeline. The publisher of the message has an expectation about how the consumer handles the message. A contract exists between the two sides. A Message - DO SOMETHING or GIVE ME SOMETHING.
An example: the publisher sends a message with the raw data, and expects the consumer to create a file from that data and send a response when the work is done.
