What are some things he can see from the vents in his room?

In the story, Luke must hide in the attic, as he is an illegal third child. The attic doubles as his bedroom and playroom. In fact, it is the only room in the house that can keep Luke safely hidden.
For his part, Luke despises the attic. There are no windows there, which means that he gets few glimpses into the outside world. So, Luke is very excited when he discovers that there are vents in the attic roof, one at each end.
From one of the vents, Luke can see a small strip of road and the cornfield beyond. The other vent faces the backyard. From this second vent, Luke is able to see the woods near the house. He is shocked when he looks through this second vent: the acres and acres of land that were once filled with trees are being cleared.
Construction crews are everywhere; from his vantage point, Luke can see bulldozers, backhoes, and trucks. Luke eventually discovers that new houses will be built on the cleared land.
On another occasion, Luke is able to watch his father and two brothers (Matthew and Mark) load the family hogs onto the livestock trailer. Sometimes, Luke also gets to watch his brothers climb onto the school bus in the mornings. After the new houses are completed, Luke is able to spy on his new neighbors. This is how he discovers Jen, another third child in the neighborhood.
The vents basically allow Luke glimpses into the outside world.