Headers Hold Details Like the Body's Format, Size, and Sender
Each header line states one piece of information about the request or response itself, separate from the body's actual content.
Content-Type indicates the body's format, Accept says which formats the client is willing to receive back, Authorization supplies the client's credentials, and Content-Length indicates the body's size in bytes.
Content negotiation is the server reading Accept and choosing a response format the client asked for, rather than always answering in the same format.
GOAL
Explain what Content-Type, Accept, Authorization, and Content-Length each do, and how content negotiation uses Accept to choose a response format.
A client sends Accept: application/json with its request. What does that header tell the server?