Contextual advertising is different from search advertising in important ways. The document outlines several key differences between contextual and search advertising, including that readers are not actively searching for advertisers, keywords work differently by focusing on themes rather than discrete entities, ad copy needs to stand out more, and magic ad positions are 1-4 rather than 1-3. The document provides advice on setting up separate contextual advertising campaigns, testing ads, and using Google's Placement Performance Reports to refine site targeting over time.