The document discusses the evolution of search engines through different generations, with the 3rd generation aiming to use natural language understanding to think more like humans. It notes 1st generation search was specific and forced, 2nd generation added boolean logic and keywords, and 2.5 generation included tagging, clustering, and comments. The 3rd generation focuses on natural language to understand grammar, vocabulary, and context like humans through knowledge databases and user participation. It concludes by questioning if search engines could truly think like humans.