The document discusses the evolution of search engines from first generation keyword-based systems to modern personalized and social search. First generation search relied on analyzing keywords on webpages, but led to spamming issues. Second generation introduced factors like clickthrough rates and PageRank to rank pages. Third generation includes personalized search that tailors results based on individual user preferences and search/browsing history. Social search aims to incorporate social connections and activity into rankings but has faced challenges in implementation. The future may involve search becoming more integrated with social networks like Facebook or shifting towards discovery-based models.