A jms message has three components

1. A header
2. Properties (Optional)
3. A body (Optional)

Message header

For message identification. For example the header is used to determine if a given message is appropriate for a subscriber

Properties

For application-specific provider-specific and optional header fields

Body

Holds the content of the message. Several formats are supported including TextMessage which wrap a simple String that wrap arbitrary Java objects (which must be serializable). Other formats are supported as well.