The core function of a search engine is to index and retrieve information from the web, providing users with relevant results for their queries. When users input search terms, the search engine algorithms analyze indexed data to return a list of pages that best match the query's intent. This process involves crawling websites, ranking content based on relevance and quality, and continuously refining algorithms to enhance user experience. Popular search engines like Google utilize advanced technologies, including machine learning and natural language processing, to improve search results.