1. Messages are the unit of communication in chat models.
2. They are used to represent the input and output of a chat model, as well as any additional context or metadata that may be associated with a conversation.
3. Each message has a role (e.g., "user", "assistant") and content (e.g., text, multimodal data) with additional metadata.

A message typically consists of the following pieces of information:

• Role: The role of the message (e.g., "user", "assistant").
• Content: The content of the message (e.g., text, multimodal data).
• Additional metadata: id, name, token usage and other model-specific metadata.

Role:

1. Roles are used to distinguish between different types of messages in a conversation and help the chat model understand how to respond to a given sequence of messages.

Content: The content of a message text or a list of dictionaries representing multimodal data (e.g., images, audio, video).

• SystemMessage -- for content which should be passed to direct the conversation
• HumanMessage -- for content in the input from the user.
• AIMessage -- for content in the response from the model.
• Multimodality -- for more information on multimodal content.

Other message data:

Depending on the chat model provider, messages can include other data such as:

• ID: An optional unique identifier for the message.
• Name: An optional name property which allows differentiate between different entities/speakers with the same role. Not all models support this!