A ghostwriter is a professional writer who is paid to write books, articles, stories, reports, or other texts that are officially credited to another person. wikipedia.org

Fiction writing is the composition of not factual texts. Fictional writing often is produced as a story meant to entertain or convey an author's point of view.

Creative writing is considered to be any writing, fiction, poetry, or non-fiction, that goes outside the bounds of normal professional, journalistic, academic, and technical forms of literature. Works which fall into this category include novels, epics, short stories, and poems. wikipedia.org

Worldbuilding is the process of constructing an imaginary world, sometimes associated with a fictional universe. It describes a key role in the task of a fantasy writer: that of developing an imaginary setting that is coherent and possesses a history, geography, ecology, and so forth. wikipedia.org