“Prompt engineering” sounds like a specialized technical skill. Mostly, it is just being specific.
Vague requests get vague answers
“Write about dogs” and “write a 200-word intro for new dog owners about crate training” produce wildly different quality — the second simply removes ambiguity for the model.
Examples do a lot of work
Showing a model one example of the format you want often outperforms paragraphs of instructions describing that format abstractly.
The actual skill
It is closer to writing a clear brief for a very literal-minded collaborator than to programming in the traditional sense.