Not a breeze can stir but it thrills us with the breath of autumn. The Old Manse (From Mosses From An Old Manse) Nathaniel Hawthorne Her stiff cap moved in the breeze as it swung from the corner of her mirror.
1. a slight indentation or depression, as one produced in the surface of one organ by pressure exerted by another. 2. a negative imprint of an object made in some plastic material that later solidifies. 3. an effect produced upon the mind, body, or senses by some external stimulus or agent. basilar impression.
An impression (in the context of online advertising) is when an ad is fetched from its source, and is countable. Clicking or not is not taken into account. Each time an ad is fetched it is counted as one impression.