Editorial captions provide information and context about the image to the customer.
Captions answer the five W questions: where, when, what, who and why. People seeing your image will ask all of these questions. In a few sentences, provide the background information necessary to describe and explain your image. Captions short be short, concise, and accurate. Stick to the facts and quickly explain what it is you've shot.
Here are some examples of good captions. They don't need to be overly long, just specific and to the point.