If I'm writing about, let's say, two people having a conversation while they take a walk through Victoria Park in Hong Kong, I'll picture the exact path where they walk, even if it's never mentioned in the story and doesn't make any difference. It's better for me if I can see them near the model boat pool or wherever. If I can't picture it my head, I'll look at photographs I've taken over the years. Even if the photograph doesn't show the entire area, it will remind me of everything nearby. Photographs you take yourself are a million times better for recall than online photographs.
I don't know what science fiction writers do when they're writing about alien planets. I'd probably have to draw some rudimentary landscape so at least I know how everything might look.
If anyone knows who the artist is, please let me know.