Chat Markup Language - the division of the conversation with GPT into system, user and assistant prompts.
From the model's perspective, it's still one block of text described by metadata. We should consider it as a whole as well.
Due to that, we don't have to define each field every time. This perspective can help us to design prompts that fit the model's way of working, potentially improving overall model's effectiveness.
Issues
The gpt-3.5-turbo occasionally has issues with following the system instructions. In such cases it's wiser to provide the instruction in the user field.