developing ideas
Lots of people have ideas. Writers develop ideas.
I have just finished a book about computing, by a computer expert, not a writer. It was long winded and didn't say much because the ideas, and there were some, were buried, thrown away, not developed. One was: what if you designed an operating system without files. Are files as integral to computing as we think? This idea- which is interesting and kind of amazing (apple's very first OS tinkered with a no files concelt until Steve Jobs decided to embrace them) is just left hanging out to dry.
Taking an idea and turning it over in your palm, as a diamond cutter turns over a gem, looking for lines of interest, where it will crack open, what potential jewel is hidden within- all this the work of the writer.
Often writers have LESS ideas than normal folk. But they are good at spotting good ones, stealing them and running with them. Unpacking is mainly what writers seem to do.