What is a message?
A message is a communication asset used to transmit or exchange information from a sender to the receiver through channels. A single message can be consumed by multiple independent receivers and can also be defined as an event or command. The sender includes a payload of data that needs to be processed and serialized by the receiver into an appropriate format, e.g., JSON, XML, binary, etc. It may also include metadata, i.e., information that describes the message itself. This metadata is often known as headers or properties.
In the diagram above, the sender application transmits a message to the receiver application.
Messages vs Events
A message carries information from one application to the other, while an event is a message that provides details of something that has already occurred. One important aspect to note is that depending on the type of information a message contains, it can fall under an event, query, or command.
See the diagram below.
Overall, events are messages but not all messages are events.
