So how does description create a dominant impression? Well, you have to choose carefully what to include and what to omit. Then you have to weigh your word choices carefully to make sure that every word contributes to the overall effect you're striving for. Let's "look" at the park again and imagine it's a chilly, late autumn day. Then consider the following description:
Children laugh and squeal as they play on the frosty jungle gym, puffs of their breath visible in the crisp autumn air. Young girls chase one another around a silver-branched birch while their parents sit close by, talking and sharing the steaming contents of their thermoses. A pair of elderly gentlemen play chess on the sidelines, blowing on their hands occasionally to warm them.
What's just been described reads like a happy scene, where people are having fun and interacting peacefully. But you could describe that same setting and create an impression of loss and loneliness, perhaps even fear:
Children scream as their bare hands grasp the icy iron bars of the jungle gym. A group of gray-coated girls chase one another endlessly around a bare-limbed tree, kicking up dust from the parched ground and stirring piles of dead leaves. Parents perch stiffly on nearby benches, hands curled around mugs of coffee that chills too quickly to keep them warm. On the sidelines, two old men huddle over a chessboard, stealing occasional glances at the children and muttering.
Same landscape and essentially the same details, but the dominant impression sure is different, isn't it?