If we think a part of the world is really important, and we want our reader to be able to see something specific in their mind’s eye, then we can expand the description.
Here's another snippet from Grace Lin, and it also describes a forest, but this description expands on detail:
And he brought me to a part of the forest I had never seen before, a part I don’t think anyone from the city has ever seen before. The trees seemed to reach the clouds, the green grass felt like a silk blanket, and there was a lake of clear water, so pure and clean it looked as if it were a piece of the sky.
In this snippet, the forest is really important. Grace Lin wants us to see how beautiful and special it is, so she describes the isolation, trees, grass, and water in detail.
Here are some more examples of expanded description.
The others drifted away, to their own homes. Dirt track gave way to cracked asphalt, loose scrub to burned out lawns, long dead under the scorching sun.
Gustav led the horses past the bakery. Fuzzy windows and faded brick hid from view the magic that lived inside. Baskets lined the walls inside, suspended at three convenient heights, filled with breads and pastries of every conceivable shape, size, and texture.
