What is creative writing? asks a student. He means, as opposed to any other kind of writing, and behind his query is a concern that his might not be creative enough.
It's not an easy question to answer. It is certainly not to do with subject matter, you can write creatively about a computer chip and equally un-creatively about a sunset. It has more to do with how the writing is constructed; whether there is attention to rhythm, word sounds, sentence or paragraph length, whether there is descriptive detail, emotional appeal.
But there is something additional to this. Something visceral, which comes from the core of the writer and speaks to the core of the reader. An authenticity, an honesty to the writing voice.
Now that is more difficult to define and explain, as it is so much more noticeable when it is absent.