As the name implies, "science writing" refers to any form of writing that communicates scientific subject matter. Science writing can take on many forms depending on its topic, purpose, and intended audience.
While traditional forms of science writing primarily involved communication between scientists, science writing is now understood to include things such as scientific proposal writing, science journalism, traditional scientific papers, and even academic textbooks. Thus the intended audience can range from experts in scientific fields to the general public. Recent communication regarding COVID-19 would classify as science writing for a public audience.
Because science itself is so broadly defined, almost all written technical communication artifacts classify as science writing in some way. The underlying thread is that all science writing must be evidence-based. Fictional writing, as well as writing about assumptions, abstract ideas, predictions, or opinions do not classify as science writing.
Despite its breadth, there are several important themes and concepts that apply to all types of science writing.
A few well known examples of science writing would include almost anything in National Geographic, all Nature publications, and this COVID-19 related infographic.